Acquire a clarinet.
Find some "premium" cork grease.
Apply the cork grease to all four corks.
Then, grab the bell.
Connect the lower joint to the bell.
Connect the upper joint to the lower joint.
Make sure that the metal keys on the side overlap.
Then, attach the barrel to the upper joint.
Makes sure there is no space between each joint.
Then, push the mouth piece onto the barrel. Make sure the flat part of the mouth piece is facing the back.
Grab the reed. Check to see that there are no chips or broken areas. This will affect your playing, and not in a good way
Line the reed up with along the flat part of the mouth piece.
Place the ligature around the mouthpiece and the reed.
Then tighten the ligature so the reed stays in place.