Set the pins of the squat rack just above your hips.
Start lighter than your squat 1RM. About 25% is a good start.
Hook the weight with your elbows. Keep your forearms pointed up.
Step out from the rack, set your wide stance with your feet flared out further than normal, inhale deeply, and brace your core.
Keeping an upright posture and a near-vertical shin angle, lower yourself towards the ground. You may not reach full depth or even hit parallel the first few times, but stick with it.