it should already be in the base plate? remove the screw and see if there if a hexagonal insert in the base plate? if there is loosen the other screws on the base plate, stick the correct size allen key in and wind it around till you feel pressure and the base plate is lifting, if not loosen the screws set the rail level and place a couple of washers, packing shims (should be able to get some from a good diy store) under the base plate to pack it out to hold it in that position, I always set the rail with a very slight lean back, this takes up the slack in the rollers, carriage and chair and lets it run level when you are sitting on the lift
