Next finding switched power. First you will need a fuse tap and an appropriate fuse. I used 5Amp because i plan on running future lighting off this same circuit. But if you plan on using just your rd i would go with 1 or 2 amp.
I also like to wire this up with a switch for convenience, but that is up to you.
There is good switched power on the P18 circuit.
Remove the fuse and insert it into your fuse tap. Make sure the 20A fuse is still the main fuse for the circuit.
In order to fit the fuse tap into place you will need to remove the trunk relay and trim the plastic as shown. I used side cutters but whatever works for you.
Now install the fuse tap and then the relay back into place, you will have to bend the fuse tap a little bit. It's a snug fit.
Check with circuit tester for power.
I installed a switch under the dash by drilling a 1/2inch hole and mounted a rocker switch.
Then i used the large 13mm bolt as ground
Hook everything up and it should power your rd.
I like putting quick connects on everything including the telephone cable, then everything is clean if i have to take everything apart later. But thats just me.