Open the trunk, and remove the floor of the trunk from the black plastic wall of the rear of the trunk (might not even be attached). Right about where the floor meet that wall, there should be two screws to remove. Next remove the the two square plastic panels on that wall. Under those panels there should be two more screws holding the wall on, and remove those. After those are removed you should be able to remove the rear wall just by pulling up a bit sharply (there are some tabs that hold it in on the top, but if you jsut pull they come out). Next you remove the nuts holding the rear "CRX" panel on. there should be, if i remember correctly, 13 nuts. Six on each side, and in the middle there is one, in this indented part of the metal. once those are removed you should remove the two grey clips supplying the power to the reverse lights. You have to press on a small tab in order to pull our the grey plugs. Now just hit the screws that the nuts were connected to with the end of a screwdriver, or something hard, and the rear panel should come right off.
You may have to knock off the plastic flap if it is in the way, with a hammer. measure two dots right over the center of the letters "C" and "X". Use a drill bit that's about 1/2", or whatever the size of the light fixtures you bought were. Drill them through, but be careful to not tap the out plastic, causing it to crack. If needed, you might have to drill a small hole in the corner or on the side to get some of the plastic's dust out of the casing.
Next you have to remove the two brake lights by pulling off the plastic coverings behind them. They each are held on by 6 nuts which you have to remove, and also they each have a grey plug which removes the same way as the reverse lights. Once you have removed the brake lights, clip the two wires connected to the parking light. Use wire clippers to strip the ends of the wires you have clipped, for like 3/4". take two pieces of wire, about 1 1/2-2 feet long, and do the same to their ends. Take a butt connector, and put the end of the wire connected to the power for the light, and put in the other end, the corresponding colored wire for the parking light, and also the new wire you have. You will probably want to twist the wires to help them fit in the connector. and then pinch the connector, so they are in. do the same with the other wire. At the other end of the wire, connect the wires with the wires of your new lights, with the corresponding colored wires. You may want to cover all connectors with electrical tape to be safe.
Do that with each brake light, and then fit the lights into your drilled holes, and if they were not correctly drilled, you may have to help them be held on with some duct tape or electrical tape. The best thing to use to keep the lights in place is some good old auto silicone, this will prevent the lights from moving and also seal it so water doesn't get in. Sometimes if the lights are shoved into the hole too far they may blink, or turn off sometimes.
Once finished, reconnect all lights, plugs, and panels with the nuts from before, and then replace the plastic wall on the back of the trunk, and your new lights should turn on whenever you have your parking lights on or your headlights on.