Place the heel of your hand on the centre of their chest.
Place your other hand on top of your first hand.
Join your fingers.
Make sure your shoulders are above your hands.
Using your body weight, press down on their chest.
Release your weight.
If they start breathing put them into the recovery position.
Lay them down on side, left leg down, right leg bent.
Right hand under chin to keep mouth open.
Left arm bent to prevent rolling over.