you just bring them with you. it will probably be really windy as always out in the middle of nowhere. some ppl really set up shop over there with chairs, cabanas, hammmocks, the whole sha-bang. if you were to bring spectators make sure they wont be just standing out in the wind all day!
there is a $10 entry fee at the track. but i dont knw about those that are just coming along as Ive only driven to events by myself.