1) Find the parallel dip bars. If the width of the bars is adjustable make sure that they are at shoulder width.
Grab the bars and lift yourself in the air. Keep your feet together and contract your glutes and abs to stabilize your body.
This is your starting position.
2) The goal of this exercise is to remove the stress from the chest and focus more on the triceps.
When you are lowering yourself keep your head and chest up and keep your elbows close to your body. Overall, your goal is to keep your torso upright.
Looking straight forwards, instead of down, helps retain your upright position.
Slowly lower yourself to where your elbows are at about 90°. If you go a bit further than that, that's fine. But the lower you go, the more you target your chest and not your triceps.
3) Push yourself back up to your starting position. When at the top do not fully extend your elbows and keep a slight bend.
If you lock your elbows you remove the tension from the muscle and place it on the elbow joint.