Where to hook?
Lots of good pictures on the website to look at. A really good one right now on the front page shows it well.
The trap wires have a wire thimble (loop) on the end. A line passes through that. The J&H is tied to the end of the line. A bunjee ties to the other end (and goes under the tramp to the opposite side of the boat). There would be a small black "rope lock" on the line to set the length that the J&H pulls down to (your trapeze height adjustment). Your harness should have a hook on a plate or spreader bar. The hook points down. When you sit on the side rail, you pull the J&H trap handle down and hook to the bottom of its loop. The bunjee pulles back on the J&H / line to keep tension on the system connection to your harness. This helps to keep it hooked as you move around getting out on the wire before you load you weight onto it.
Check the FAQ on trapeze.
http://www.hobiecat.com/community/viewtopic.php?t=1145