Hopefully the mast already has somewhere to attach the trapeze, should be where the sidestays attach. If not, you'll need to change that fitting.
For the actual trapeze, you need a length of 3 or 4 mm dyneema core, a trapeze cleat (RF5121), a trapeze loop/block assembly (RF17), a trapeze handle, and a length of rope (around 6mm) to adjust the height of the ring.
Then you run a length of shock cord from the trapeze ring, through a saddle on the deck, forward to a block somewhere near the bow, then back down the other side to the other trapeze.
Hopefully this makes sense!