Step 1: Log into webmail
Step 2: Under Options at the right, select See All Options.
Step 3: Click on Groups at the left of the screen.
Step 4: To add a user, select a group from under the Public Groups I Own list. You must be an owner of the group to make changes.
Step 5: Expand the Membership tab, then click Add.
Step 6: Search for the user you want to add, then click double click the name and click OK or just click Add then OK.
Step 7: Click Save.
To delete a user, select the username, click the Remove button, then click Save.