Not rocket science...
Mark the center of the new chain, mark the center of the sprocket, unscrew the two locknuts, put the new chain in place, replace locknuts with new. Tension the chain to about 1/8" sideplay.
If still in doubt, the Hobie forums have anything and everything you need to know. Start your search here:
http://www.hobiecat.com/forums/index.php?c=N