Tie a trapeze ring (dog bone) to each of the 3' lines (should have 4). Thread the line through the thimble at the end of the trapeze wire. Thread one of the plastic height adjusters onto the line, wrapping the line aroud it at least twice, this allows height adjustment for the trapeze. Tie the tail of the line to the shock cord with a bowline, then run the shock cord through the block, then through the grommet in the tramp so it leads underneath the tramp so you can pull it up through the other side and the repeat.
Hope this helps.