Chargin,

The main sheet tail that you refer to should go back through the traveler (it should have some sort of sheaves for this) and tie to the center of the rear beam on the back somewhere. You will sail using the loop coming out of the main sheet cleat and reentering the traveler cleat. This line performs both functions as the main sheet AND the traveler control - it's easier to keep up with it instead of two separate lines.

I suggest that you guys find a sailing club somewhere around you and see if you can get someone to show you the ropes - I'm certain there's a lot of people that would be very happy to do so. If you are unable or unwilling to do so be sure you understand the basics of sailing upwind and downwind and be CERTAIN that you have a good plan for righting the boat if you capsize. There are a lot of threads here about the proper way to right a catamaran - there are some tricks to it.