I'm presuming that you're wanting to set a tracker to your profile that allows folks to join via your link/tracker?
If so, sign out, go to the 'join hubpages' page. Copy the url. Sign back in. You need to insert your tracker into the url you just copied. The attach your tracker to that. Then insert THAT into your prfile. It should look something like :
http:// hubpages.com/ _yourtracker / user/new (minues the spacing)
Do it as a text link, so it looks less messy.