Log into https://app.onsip.com/. On the right side of the screen select “Administrators”. Select “Inbound Call Settings” to the left, then choose “Groups”.

Next, on the right side click “Add Group”. In the Basic Settings, you will give your group a name, set the ring strategy, the ring duration, add extensions and phone numbers for your group.  Simultaneous Ring will ring all users in a group at once, while a Hunt Group will ring each user in sequence.

Click Next to go to the Add Users tab. Here you can add users to the group by searching by the name in the search option at the top or clicking on the checkbox by the name below. Hunt groups members will ring in the order the users are checked.

To proceed to the final review, click Next. From here you can make any final edits if needed, Cancel go Back or Safe & Finish Setup.  

If you need to later modify your group, navigate to the “Inbound Call Settings” then "Groups” and click the name of the group. You will be presented with the group's details.

Click "Edit Info" to make any changes or click the  icon to permanently delete the group. Please be careful when deleting groups, as they cannot be recovered.

Limits to Groups, see this link for Groups.