Can I start playing football now?

Yes, you can. How can you run cross country and play soccer? They're in the same season. You can't bench press 180 lb. If you're extremely fast in cross country you aren't extremely fast for football and vice versa. Your coach will put you at a position best suited for you and the team. No one here can tell you what position to play. No one here has any idea what kind of athlete you are. Since you know nothing about how to play a position there's no point in going to a camp. Few camps, if any, would accept someone with no experience, anyway. Just do a lot of running and get into really good shape. Be sure to eat healthy.