First, add [XF] to your name. That way, if you can't get the 'join group' to work (like you told me earlier) you will at least be seen by others as an X-fusion.
To join the group click 'join this group' in this page: http://steamcommunity.com/groups/X-FUSIONisWin/
It may not ever change even if you do join the group, so just look for your name under 'members' near the bottom of the page.