Go to Admin Menu > Groups > Group Types.
Once on the Group Types screen, you'll see that there are no group types yet.
Click the Add Group Type button to start one up.
Name field = Service.
Description field = enter some descriptive text.
The Group Creator Automatically Becomes a Member checkbox = leave checked.
Group Creator Must Complete their Membership checkbox = leave checked.
Automatically Configure an Administrative Role checkbox = check this.
After checking it, another field will appear.
Automatically Assign This Administrative Role to Group Creators checkbox = check this.
Click the Save Group Type button.
Upon saving, you'll be redirected back to the Group Types screen.
Your new Service group type will appear in the list.