This is a variation of the conventional deadlift and some people find that they are much stronger in this position.
Begin by placing your feet under a loaded barbell with a stance that is wider than shoulder width apart. This is the main difference between the conventional deadlift and the sumo deadlift; some will go to extreme widths, but start with a stance slightly wider than your shoulders. Your feet should still be halfway under the bar and your toes should be pointed slightly out. Begin by squatting down through your knees and grabbing the bar. Your hands should be inside your legs and your arms should be locked out and hanging straight down. Keep your back straight and tight. Begin the movement by pushing through your legs until your legs are locked out. Keep your back straight throughout the movement, and there should be little movement of your torso as long as you keep your core muscles contracted. Squat back down through your legs and return the bar to the floor. Repeat this movement until you have completed your set.
This variation will use more leg drive to get the bar moving, but your back must be very strong to hold the upright position during this movement.
Keep your back straight throughout this movement; do not allow it to round at all. This may cause injury.