For the first triceps (the muscle at the back of your upper arm) exercise:
Sit with good posture in a chair, holding a dumbbell in your right hand
Raise the dumbbell above your head, and stabilize your right arm by placing your left hand on your right elbow
Slowly bend your right elbow, lowering the dumbbell down behind your head
From that starting position, raise the weight toward the ceiling, and then gently lower it back down behind your head
Repeat 10 times then switch arms.
Rotate your shoulders a few times to loosen any tension.