Quilly , being that your just getting into archery , I would suggest working strictly on your form before putting much attention on equipment adjustments. Assumeing you had your rest installed at a proshop , everything should be set correctly. What your describing (shooting to the left occasionally) sounds like it could be a anchor problem. Work on getting good form with a rock solid anchor first and everything will fall into place.
What do you use for an anchor point? Example: I use a kisser button in the corner of my mouth , the tip of my nose on the string , and my release hand on the bottom of my jaw. All of these little things help in achieving a consistant anchor point. It's alot like bowling , you work on form , then work on doing the same exact thing on every shot.
Hope this helps!

<---Doug---<<<