Grab a bar with appropriate weight while standing upright, narrow grip (that could mean handes 6 inches apart). You should be holding it, arms unflexed, legs maybe shoulder-width. Like the lockout position for a deadlift. Bend over at the waist so that your back forms roughly a 60 degree angle with the horizontal, and pull the bar from a hanging position to your lower chest/upper ab area. Lower it for a controlled eccentric.
Note: keep your spine erect during the movement. I was gonna show you the one on exrx.net, but I don't like that one because he starts it from the floor and bends his spine.
-Calkid
