I just added an XBox Live leaderboard. To add your gamertag, all you need to do is
* go to your User CP > Edit Details > then enter your gamertag down in the additional details section.
You can view all of the BCP gamertags entered along with their scores at this link --> http://bobcatsplanet.com/vb/gxboxlive.php you can also get to it from the leaderboard link at the top of the page
Let me know if you have any questions.