Lift up on the covers on the regular toilet seat installed on the toilet, exposing the plastic bolts hidden underneath. Insert a screwdriver into the slots on the bolt heads and grab the nuts located on the other end of the bolts on the underside of the toilet bowl.
Twist the screwdriver counterclockwise until the nuts unthread from the bolts. Remove the bolts from the toilet bowl and lift the seat off the bowl as well.
Turn the adjustment handle on the raised toilet seat counterclockwise until loose, if a handle is present. Place the seat onto the bowl so the tall end of the seat is in the rear and the seat sits on the edge of the bowl's opening, then press down on the seat so it sits firmly in place. If the seat is adjustable, make sure the rear tabs on the seat are inside the toilet bowl.
Use your hands to turn the knob on the toilet seat, if present, clockwise until you feel resistance. Turn the handle another one-eighth of a rotation.