Not really a hard tech question, but it can be frustrating so I will answer it anyway.
It is under the dash right right by the driver's side kick panel. It runs in line with a harness and doesn't have a large mount or anything like the underhood relays. When mine went out I crawled up in there and kept hitting the horn and feeling for the clicking on the relay until I got it. If you need a picture PM me and I will try to run out there with a camera.