Lift the Explorer's hood to access the battery. Peel the black rubber covering away from the negative battery terminal.
Place a 10 mm wrench around the negative battery cable bolt. Rotate the wrench counterclockwise to loosen the cable's clamp from the terminal post. Remove the cable from the battery post. Move to the inside of the Ford.
Place the faceplate adapter into the vacant stereo mounting dock. Slide the adapter into the opening until it locks into place. Reach into the back of the dock to pull the stereo wiring and antenna cable forward.
Plug the white plastic wire binders that group the Explorer's stereo wires together into the corresponding connectors of the wiring harness adapter.
Insert the wiring harness adapter lead connectors into the appropriate outlets on the rear panel of the aftermarket CD player. The harness will have clear markings to illustrate where the connections will be made.
Plug the Explorer's antenna cable into the FM antenna outlet on the back of the CD player. (Most stereos will have the antenna outlet on the right side of the rear panel of the outlet.)
Slide the CD player into the faceplate adapter's opening. Push the unit into the dock until it locks into place.
Place the negative battery cable clamp back around the negative battery post. Tighten the bolt on the clamp to secure the cable to the terminal post. Replace the black rubber covering over the terminal and close the Explorer's hood.The 1999 Ford Explorer's stereo deck can be taken out using Ford DIN removal keys. These special tools are inserted into the holes on the face of the stock deck to extract the unit from the dashboard stereo dock. Installing a new CD player requires putting in a faceplate adapter to fit the new deck into the stereo mounting dock. You will also need to use a wiring harness adapter to level the compatibility gap that may exist between the Explorer's wiring and the CD player's rear panel outlets.