The sumo deadlift is safer than the conventional deadlift because you're in a wide position and it allows you to focus on the posterior chain instead of the lower back.
Space your feet out wide with toes pointed out. Grip the bar so that some of your hand is touching the knurling, where the smooth meets the rough part of the bar (on most bars).
Get into the set-up position and execute the lift by driving the knees out like you're spreading the floor with your feet. Brace the core and finish with the glutes.