See also the official documentation:
Help Center > Group Owners Manual > Premium and Enterprise member management options > Adding members directly
Direct Add members
(Premium or Enterprise only)
About Direct Add
Direct Add is a feature available only to Premium and Enterprise groups, see Pricing.
If your group is Basic (free) there is an option to upgrade to Premium for one month, automatically reverting to Basic after 30 days; see the Upgrade link in the Admin section in the left column of your group.
The cost for that is the same as one month of Premium and may be well worthwhile if you have a large number of email addresses you wish to add to your group.
List of Email Addresses
On the Direct Add page you will be asked to enter a list of email addresses (plus optional information), either by typing or pasting the list into a text box, or by browsing to a file on your computer containing the same information:
The three fields of information you may enter for each email address are:
Display Name — Optional. If present it is first on the line and must be separated from the Email Address by a space character. The Display Name may contain one or more space characters. This is the human-friendly name that will be shown for the member next to their postings and elsewhere on site. It is usually (but not always) present for each member in the export from a Yahoo group's Manage Members page.
Email Address — Mandatory for each member to be added. This is the key information available from an export of a Yahoo group's Manage Members list. It may stand alone on the line, but if other information is included then the Email Address must be delimited by angle-bracket characters (also known as less than and greater than) on both sides, as shown in the example on the screen shot.
Email Delivery — Optional. If present it is last on the line and must be separated from the Email Address by a space character. This information is present for each member in the export from a Yahoo group's Manage Members page; it is identified as the Delivery column, but the literal text to be used in the Direct Add page differs from the text exported by Yahoo. Also, Direct Add supports a limited set of values.
Posting privileges (moderation):
The Spam Control section of Settings controls the posting privileges of a Direct Add'd member (or any new member except one transferred from a Yahoo Group).
The privileges are set to:
o "Use Group Moderation Setting"
or
o "Override: new member moderated" - the member's messages are moderated until "Unmoderate After" number of that member's messages have been approved.
Instructions for creating a list in Excel
Altering a Yahoo Group member list Export for the “Direct Add” function at groups.io
These are the steps I used to prepare a text file suitable for upload into the “Direct Add” member subscription function.
1. Export the Y! member list to csv format. (Yahoo will only export the first 1000 members – there are other options if your group has more than 1000 members.)
2. Open in Excel
3. Insert a new “Column A” to contain the text string “Direct Add” expects.
4. Insert a new “Column D” to contain a translation of the “Delivery” field to the keyword expected by “Direct Add”
5. In my case, this resulted in a spreadsheet format as follows:
Column A: container for “Direct Add” lines
Column B: The Display Name from Yahoo
Column C: The email address from Yahoo
Column D: container for the “Delivery” option converted from Column G to the keyword “Direct Add” expects
Column E: Joined date from Yahoo – not used
Column F: Member Status from Yahoo – not used
Column G: Email Delivery option from Yahoo, converted in Column D to the keyword “Direct Add” expects.
Column H: Posting status – not used.
6. For later convenience, I then sorted on Column F (descending) (to place non-member roles at the top), then on Column G (to group like delivery options together), then on Column C (to alphabetize member email addresses).
7. Paste the following formula into cell D1 and then copy it down through Column D for each entry. I know that ‘special’ is not a currently supported keyword, but in my single-email test it was just ignored, and I could manually update from “Individual Emails” to “Special”. However, when the “Direct Add” file I created here was processed after I uploaded it, the “Special” members were already set to “Special” in the group member list.
=IF(G1="Individual Emails","",(IF(G1="Daily Digest","digest",(IF(G1="No Email","nomail",(IF(G1="Special Notices","special","SomethingElse")))))))
8. Paste the following formula into cell A1 and then copy it down throughout Column A for each entry:
=CONCATENATE(B1," <",C1,">"," ",D1)
9. Check the contents of Column A closely, to confirm each line is the format expected by "Direct Add".
10. Highlight all the contents of Column A. Copy and paste it into a text file (I use Windows Notepad to be sure no non-text characters are carried forward.)
11. I saved and uploaded this file to the “Direct Add” page.
There is also another Chrome-browser specific procedure to download group membership data that includes additional data fields, available at the link below.
http://yahoogroupedia.pbworks.com/Chrome+Application+to+Download+Members
The official Groups.io user documentation is in the Groups.io Help Center.