Before you even get on a boat you need to know how To Sail and To Tie The Knots that are required to sail. You also need to know about Safety Of A Sailboat. It is also a good idea to know The Parts Of The Boat.
Your boat will be attached to a Dock. If you know the parts of a sailboat you will probably be able to identify all of the parts of the sailboat. Your guide (if you have a guide) will tell you how to start out sailing. If you have read How To Sail you will probably already know most of the stuff he is telling you. The first time you sail you will probably be doing the basic things like knowing what to do if the boat falls over and the different sailing maneuvers.