Unfortunatelly there is no standard way for an extension to inject itself in the user profile so to get the groups tab there is some more work to do.
Edit XWiki.XWikiUserSheet document and add the following line:
#set($discard = $categories.add({'id':'groups', 'sheet':'XWiki.XWikiUserMembershipSheet', 'glyphicon': 'modal-window'}))
Since 10.8RC1 this feature is part of XWiki Standard.
If it is included qhy we need to add this line? And what exactly mean: Edit XWiki.XWikiUserSheet
? How to get to this page?
WIthout this line I have empty groups