Grasp the barrel with your right hand and the thumb pointing at the end you will insert the mouthpiece. Grasp the mouthpiece in your left hand with your thumb poiting at the reed end of the mouthpiece. Slide the mouthpiece cap over the reed and assembled mouthpiece to protect the reed while inserting the mouthpiece in the barrel. Gently tighten the ligature screws down so it holds the reed firmly in place with the tip of the reed just matching the tip of the mouthpiece. Wet the reed with your saliva and then gently and carefully slide the reed under the ligature so it rests on the flat surface of the mouthpiece with the thinnest end facing the tip or end that goes in your mouth ( not the cork end). looking at the squarish hole that the reed covers slide the ligature(looks kind of like a hose clamp, is metal with usually two screws to tighten) over the mothpiece with the screws on the hole side. Make sure you have a reed that is the correct strength for you. The reed should be on the bottom looking down the clarinet when it is assembled. If it is too loose you will need it to be recorked but you might get away with wrapping a strip of paper over the cork as a temporary fix. Some cork grease (a small amount rubbed on the cork will help it slide in easier. I recommend putting the reed on the mouthpiece before you insert the end of the mouthpiece in the barrel. First you need to have the barrel inserted in the top joint of the clarinet.