How to do... a tricep push down
A tricep push down is a great exercise specifically to target your tricep (the muscle down the back of your arm)
Here's how you do it.
Find the long bar cable attachment
Select the weight suitable for you (start off light until you get the form right)
With an over hand grip, pull the bar to your thighs, keeping your elbows close to your body
Keeping your elbows still, lift your forearms to your chest
Keep your chest lifted, head up and abs tight
Push the cable back to your thighs (elbows in!)
Repeate - remember only your forearms should move!