If you've been approved as a Sith then you should look into the forums there for things your character can do as training. Otherwise you can try joining one of the Open threads in the main Story or creating one of your own. Really it is at your own discretion where you decide to begin.
EDIT: Go here to sign up your Sith character if you haven't done so yet. And be sure to give some of the guides a good read. There are some guidelines towards Force powers and others have strict rules because of the lack of defense against them for Non-Force sensitives.