The center seating position for the Mega Cab and Crew Cab front seat has a lap belt only. To buckle the lap belt, slide the latch plate into the buckle until you hear a "click." To lengthen the lap belt, tilt the latch plate and pull.
To remove slack, pull the loose end of the webbing. Wear the lap belt snug against the hips. Sit back and upright in the seat, then adjust the seat belt as tightly as is comfortable.