Anchor resistance band low behind you (or lie on it).

Lie on back, hold band ends/handles.

Extend arms straight up over chest/face, elbows pointing up.

Keep upper arms stationary.

Lower hands towards forehead/shoulders by bending elbows, stretching triceps.

Extend elbows to push band back to starting position, contracting triceps.

Maintain control throughout. Repeat for desired reps.