Installing a 4 prong dryer plug
the difference between a 3 wire and a 4 wire connection on the dryer is the white (neutral) and the ground (green, bare, or green w/ yellow stripes) are connected to the same terminal of the cord with a 3 wire. With a 4 wire, those 2 are separated and each connect to the respective wire of the cord.
Usually, on the newer dryers, there are 4 terminals and you just connect the cord as required; 2 hot wires (black, red) to the brass screws. Neutral wire to silver screw and ground wire to green screw.
what you need to do is look for a bonding strip that runs from the neutral terminal to the ground terminal or to the frame of the dryer. That bonding strap would need to be disconnected so as to separate the neutral and ground terminals.
if you can take pics of the dryer, it might make it easier to explain to you.