I dunno what year you have, but in earlier ones (prob all 1Gs), the seat bottom disconnects with two latches under the seat bottom (near the front). If you lift it out, you'll get at the seatbelt "sockets" (the part that accepts the belt latch). Now, there's some rubber/plastic surrounding the hole in the seat bottom. Fix it, then carefully place the "sockets" through the holes, observing their travel through the holes. Once the seat is in place, with the "sockets" protruding, give the seat a good whack downwards above the latches, or sit on each side until the latches have clicked shut.
Does that help?
- b.