93 Toyota Tercel AIr Bag Light On

I have a 93 Toyota Tercel, here in Hawaii, and before I can get it registered and insuredI need to pass a safety check. The problem is, the previous owner never gave me the book, and I am trying to fix it on my own, too much money has already been spent on fixing the car, and the only problem at this point is that the air bag light stays on. If I take it to a shop, they charge for the diagnostic test fee which runs around 100 dollars or more, before they tell me how much it is going to cost to fix it. I do not want to waste any more than I have to, yet, this car is going to be meant only for a college student, and occasional use. BIG Question: How do I get the air bag light to go away, is it not a matter of just resetting it somewhere within the vehicle. Advice please.