See also the official documentation:


Customizing Your Own Account

Use the drop menu under your name, in the upper right corner, and select Account

These changes are for YOUR OWN account only, not group preferences.

(Group preferences are in Admin and available to owners, also to moderators if given permission by the owner.)

Your account page displays these options:

  1. Login - your email address - change it here. Password - change or delete. Email aliases.
  2. Preferences for YOUR account - time zone, date format, editor preference on the website, receiving your own posts by email
  3. Security - set up 2-factor authentication
  4. Identity - your profile. See details below.
  5. Other Services - oauth logins, if any
  6. Recent Bounces
  7. Billing - If you have a premium or enterprise account, your credit card on file and payment history.

Changing Your Email Address

Important - your email address is your account ID.

  1. Log into Groups.io
    Note: If you don't have a password already, you can create one from the main Groups.io page or use one of the other options (email me a link, or log in with Facebook or Google). 
  2. On the home page for your group, click on your name in the top right corner.
  3. Click Account.
  4. On the login page that appears, enter your new email address in the Email field (overwriting what is already there).
    Be careful! It is difficult if you misspell your email address.
  5. Click the Change Email button.
  6. Look for the email message sent to the destination (i.e. new) email address.
  7. Click on the link in that email to complete the change. Once your new email address is confirmed, you will again be able to participate in your groups. All your Groups.io subscriptions will be transferred to your new email address.

Adding or changing a password

It isn't necessary to set one - you can use the Email me a link. See https://groups.io/g/GroupManagersForum/wiki/Logging-In

But you can if you wish. 
Click in the empty box and a down arrow will pop up. Choose your correct email address for this account.

Type in the password you wish. Click on Change password. Caution - there is no re-type to confirm password. After the change, you will see a green banner that says your password has been updated.

Note that the box stays empty, even though a password has been set.
In spite of setting a password, you can still us "email me a link to login".

If you've made a typo in your new password (That you can't see.) use the Email me a link to log in, then be more careful about entering the 'new' password again.

Adding an Email Alias

Since your account ID is your email address, you can only email from that address, unless you set an email alias. This is useful if you wanted to email to a group from your work computer. 

Note that an email alias is a POST-ONLY address. You will not receive mail at that email alias, nor can you set up an alias using an email address that is already in use as an established groups.io account.

Your alias email address will not show on the group with your post nor in Activity  Your usual email address will be shown.

Set that up on your group site - go to your name in the top right corner

  1. Log in to your account.
  2. Select "Account" from the top right after logging in. 
  3. Scroll down to the bottom of the page where it says "Advanced Settings For Email Aliases" and click on the right arrow at the far right of that line.
  4. Enter the e-mail alias in the space below the text, then click the blue "Add Email Alias" button right below it.

Preferences

These are preferences for your own account (website preferences).

Set your time zone.

Choose time display format and calendar start day.

Editor preference: HTML, markdown and plain text. If you choose plain text, you will not get the full set of tools in the compose text box or wiki. (The owner may have made changes in Settings to disallow HTML. This will affect you.)

Items per page (displayed) and Email preference (if your email doesn't provide this).

Be sure to save by clicking Update Preferences.

Security

Set up two-factor authentication

Identity (Your Profile)

On this page, you can set a display name, tell others about yourself, and post a photo if you would like to do so.

You can set this information for the Groups.io site (your account profile) and/or for each group you're subscribed to (group profiles).

You can customize your profile for each group you are subscribed to. Changes made to your account profile will automatically apply to each group profile, with the exception of those specific fields in each group profile that you've previously customized.

Set User Name - go to Account Profile (first one). Click edit button. Your short user name. Must be unique, with no punctuation or spaces. User name will appear as @joeblow.
(Owners / moderators cannot change other people's user names.)
Note: Currently, user names have no function in Groups.io, but they might be used in the future.

Display Name - The name listed with your messages. Note: When you send a message, your email address is also shown to group members who receive messages via email.

You can customize your Display name for each group. You can only have one (1) user name.

(Owners / moderators can change other people's display names in Admin, Members. Caution advised.)

Set your profile privacy: Public, other members of your group, or only group owners and moderators.

Save changes by clicking update group profile.

Also:
Other services, your recent bounces, billing

Subscription

This refers to your own subscription for that group.  It is on the left side of a group homepage. 

Membership button

Group email address: 

Where you are now.

Email delivery:

Select email delivery. See Help Center > Members Manual > Controlling your email subscription preferences > Email Delivery.

Signature:

To set a signature for your account, go to the Subscription page for your group (it's the 'Subscription' tab in the left hand sidebar when viewing your group). On the subscription page, look for the 'Use Signature For Web Posting' checkbox and check that for adding it to web posts.  You can also add a signature to be used on posts sent via email.   If you choose either or both, then you will be able to add a signature. Once complete, click the Save button at the bottom of the page to save your changes.

Note that you can include hyperlinks and formatting in your signature. It is optional to add a signature.

Advanced preferences for email delivery - click on the arrow on the right

Also in Advanced preferences select maximum size of attachments sent to you in emails. For attachments larger than this size, links to retrieve them will be provided instead.

Click the Save button to save.

Group Profile button

You can also change your display name here (not your user name). See Identity above.
See your profile you have chosen. Edit if you wish.

Member integrations button

Member integrations allow group content that you receive to be shared with other services.

Currently (April 2020) only Google Drive is listed; however, if you try to set it up, you get this message: "Unfortunately, due to changes with Google's APIs, we've had to temporarily disable Google Drive authentication."

Email Delivery History button

See any problems or bounces

 

The official Groups.io user documentation is in the Groups.io Help Center.