1. Click this link, on the right side of the screen under "Distribution Groups I own" look for the group you would like to add the user(s) into.

2. Double click the group you would like to add the user(s) into.

3. On the right-hand side, you will need to select "membership,"

4. Once you are in the "membership" tab select the grey plus sign under "Members:" A page labeled "Members" will open up and, from here you will need to click "All Users,"

5. Insert the name of the user you will like to add to the distribution group. 

6. Once the name of the user is inserted and the user shows up, click the blue plus sign on the right side of their name. 

7. Once you have selected the user(s) you would like to add to your distribution group, click the blue button labeled "Save" on the bottom left-hand corner of the window. 

Now the user(s) selected are added to your distribution group, and you should be able to see their names under "Members:"

The selection process is not limited to one user, this may be done for multiple users at once.