Hi Jules and welcome to team TSF.
You can change teams as much as you want, but you can't carry your exisying points with you from team to team. So everytime you change teams you start at zero points.
(Unless you are returning to an old team and are still using the exact same user name. In that case your you begin adding to your original point total with that team)
You won't show up in the TSF team and stat list until you've completed a workunit.