Use the sideplate to micro-tune your arrows. Using a softer sideplate, like female velcro or a Martin rug rest, will move your point of impact to the right. Using a harder sideplate, like hard leather, will move your point of impact to the left.
If your form is inconsistent, I wouldn't worry too much about your side plate right now. For example, you might be doing any one or a combination of things that throws your arrow to the left (common). You might be able to move the point of impact slightly to the right by changing the side plate, but what you really need to do first is decide where your arrows are impacting when you shoot with good form, which you may not know yet.
For more forgiving arrow flight, make sure your arrows aren't too stiff. Good arrow tuning is the best answer.