It's true that you feel stimulation in the triceps, right? When you try to pull your elbow towards your side, you feel the triceps being stimulated, right?

Don't stretch your arms too much; just stretch them until your lats are still engaged.

How can I do it??? I understand the biceps, but the triceps...

This exercise is one that does not involve the triceps.

Reduce the weight, focus on the stimulus first, and then try increasing the weight.