Set up the squat rack so that the bar sits at about collar bone height. Place the hands either side onto the bar in an overhand grip halfway between shoulder-width and the plate. A narrower grip with your elbows pointing down will actually help keep your torso upright and make bar balance easier. This will however require good flexibility in the shoulders so start where it is comfortable and gradually narrow the grip as flexibility improves.
Pop your head under the bar and then back up on the other side so that the bar sits on the traps, just below the base of your neck. Using your thighs, drive up under the bar to un-rack the weight. Carefully step backwards with the weight on your shoulders to allow you adequate room to lunge forward. Core is tight, feet are flat on the floor. This is your starting position.
Keeping your core tight and your torso as straight and upright as possible, inhale and lunge forward on one leg and drop down until the upper thigh of the leading leg is parallel to the ground. The knee should not go forward past toe line. The knee of the back leg will stop just before touching the ground.
At this point, commence the ascent by exhaling and driving up from the heel of the leading foot and back to the starting position.
You may choose to do your lunges either stationary or walking. You may elect to focus on one side to a set before changing or alternate repetitions one side then the other.