I haven't used that particular kit, but here's my 2-cents:
the removable sheaves come apart and attach to the thimble in each trapeze wire
The trapeze line gets tied onto the "dogbone". I think you will tie off to the smaller circle and use the larger oval to hook on. I like to use a "halyard knot" which is a figure 8 stopper knot that you then tie to the dogbone with a half hitch. Some people use a bowline, but I like the halyard knot better because it keeps the dogbone snug.
thread the trapeze line from the dogbone through the sheave
thread the trapeze line through the rope lock using the guidance in this thread:
https://www.hobie.com/forums/viewtopic.php?f=14&t=50310tie off the end of the line to the shock cord (I use a bowline).
repeat on the other side.
I am not certain what those nylon washers do, but someone else may know. I'd call West Coast Sailing, they are helpful.
You'll need to experiment to figure out where to set the rope lock so that you're comfortable with the trapeze height.