Mount, top
Armbar

The classic finish from mount. When your partner pushes on your chest to escape, they hand you an arm. You swing around it, pinch it between your thighs and straighten it.
Step by step
Climb to high mount
Walk your knees up toward their armpits so their elbows come off the mat.
Trap an arm
When they push on your chest, clamp that arm to you with both hands.
Pivot and swing the leg
Post a hand on their chest, turn your hips toward the trapped arm and swing your leg over their face.
Sit close and pinch
Sit your hips down close to their shoulder, knees squeezed together. Hold the wrist to your chest with their thumb pointing up.
Lift the hips
Keep the knees tight and lift your hips slowly. Ease off the moment they tap.