The manuals are available for free to download on the Internet. Or you can simple contact Performance Catamarans out in Cali - they'll send you one. Nice people. I believe the 18 has the same setup as my 18-2. The 18-2/19 manual can be downloaded from THIS site (http://www.thebeachcats.com/index.php?module=pictures&g2_itemId=35451).
If you've steeped the mast, than you've obviously had the forestay attached. The forestay is a two-piece unit. A double short piece for the top with which one side connects to the mast tang, the other end connectes to the bigger, lower piece by a 1-inch shackle and the loose end is for the jib halyard to go through. There's a steel ring which hangs free and the connecting point. This is for the jib s-hook to hook on to. The ring MUST face inward (down).
Your jib halyard is also a 2-piece design with two brummel hooks. It runs through the ring and through the free end of the top piece of the forestay. Not this is very VERY important:
1. BOTH up and down halyards must run through the ring.
2. The s-hook must hook onto the shackle on the jib so that the open end faces down to catch the ring.
3. MOST IMPORTANT OF ALL: Test the jib halyard BEFORE you step the mast!!! The brummel hooks will NOT go through the forestay loop. If you have it on the wrong side, you will not be able to pull on the halyard to raise the jib. The idea is when you hook the halyard s-hook to the small shackle on the jib and pull it up, when it's raised, all the left over halyard line doesn't need to be coiled. You simply unclip the brummel hooks and store the halyard. So before stepping the mast, make sure that you can pull the halyard and the s-hook travels up. Discovering this after the mast has been stepped is a royal pain in the ass!
Mast stepped, shrouds connected, forestay clipped. Attach the halyard s-hook to the shackle on the jib and if there's a zipper pouch , run BOTH halyard ends through the zipper. Just hold on to the zipper with one hand as your hoist the jib up on the halyard with the other. The zipper will zip up because you're just holding it. Pull the jib all the way up and through the ring, then let it settle back down and it will hook onto the ring. Unclip the brummel hooks and stow the excess halyard. There might be a small jib downhaul string on the sail with a cam cleat on the jib. Run the string through the forestay shackle, back up through the cleat and pull tight to take out any wrinkles or slop in your jib.
Two other notes:
Ignore the manual when it says to tie a small line to your jib clew and then to the blocks. Forget it. Just shackle your jib blocks right to the jib clew itself.
Don't forget to tie a piece of bungie as a jib jam preventor. Just tie a bungie to the front crossbar, run it up and around the mast and tie off on the other side. You're making a triangle. This prevents the jib blocks from getting caught under the mast foot when you tack. It's a tiny little thing, but it really helps. It sucks to be right in the middle of a tack and wonder why you can't get the jib to come across, only to realize that the blocks are caught up in the bottom of the mast.
Hope this helps!