The Lat: A muscle with origin from the spinous processes of the lower thoracic and lumbar vertebrae, the median ridge of the sacrum, and the outer lip of the iliac crest, with insertion into the humerus, with nerve supply from the thoracodorsal nerve, and whose action adducts the arm, rotates it medially, and extends it.
Given this, you just have to add resistance to the actions. The chinup or pullup or any action that resembles such works the lats. Whether you do a chinup or a pull down with cables the action is the same. You are adducting the humerus. So when doing the exercises try to bring your elbows towards your sides, not pulling yourself up with your arms. An example would be someone doing a pull down and their forearms are in front and they seem to be pulling the bar down in front increasing the angle of the forearm and humerus. You want to derease the angle of the humerus with your side.
Many can not lift their own weight, thus chinups tend to be difficult and can overload the shoulder and lead to injury. Begin with pulldowns. Counterweigthed chinup machines are good too.
Semper Vigilo, Fortis, Paratus, et Fidelis!