The SkiErg is a great tool for total body cardio to change up the movements of traditional machines. However, misuse of any machine can lead to injury which is why it is important to set yourself up properly.
While using the SkiErg:
Stand feet shoulder-width apart, about 18-24 inches from the flywheel.
Arms bent about 90 degrees, hands above eye level.
Drive downwards initiated with a hip hinge and core engaged.
Each pull ends with arms extended to about 160 degrees by the hips, with thumbs towards the thigh and wrists flat.
Stand up, return to starting position, and repeat.
The goal is to make a smooth and continuous motion.