1- First adjust the weights of the machine to suit you, and step on it on your knees.
2- Grab the parallel handles of the bar with palms facing each other, arms fully extend.
3- Pull your body up until your chest reaches the bar level.
4- Lower your body slowly back to the starting point, and repeat.
Tips and Advices:
1- Concentrate on squeezing your back muscles while pulling your body up, don't let your biceps do all the work.
2- If you wanted to increase biceps involvement, keep your torso as straight as possible through the exercise.
Perform the tough form of this exercise if you're strong enough Neutral-Grip Chin Ups.