So you are installing fog lights, backup lights, extra auxiliary lights, etc. You want to install a switch, a toggle, a toggle switch, an on and off switch, a light switch, whatever you want to call it. You want to run the power wire from the switch to your battery. Here is a simple way to do given you have a switch and an empty spacer for a switch in your Titan. (I did this for a set of fog lights that I ran to the rear of the truck for extra backup lights - two 55 watt lights).
I recommend studying the attached images first to get an idea of what I am trying to teach you how to do.
tools: exacto knife/razor blade, needle nose pliers, file with rounded edge, 3/8 drill bit, drill, flat head screw driver, switch 20A / 12vDC
1. unscrew the two screws and then pop out the plastics (they pop out once screws are removed) under your steering wheel where the switch panel is.
2. pop out the spacer (black switch cover looking thing with nothing in it).
3. your switch won't work in the black switch spacer because it won't fit (since the hole inside the spacer has ridges, etc). just take the needle nose pliers and grab these edges and rip them off. Don't break your spacer, but you will see this is not difficult to do. The edges just bend and pull out pretty easy. Do this until you have cleaned out the insides of the spacer. File if necessary - I had to in order to make my switch fit inside.
4. the instructions on the switch call for a 12mm mounting hole. I just marked the center of the black spacer where I wanted the switch to come out and then drilled a tiny hole and worked my way up to a 3/8 hole.
5. 3/8 wasn't big enough for my hole, so I just wallered it out with a rounded file. do this slowly checking often and then repeat until your hole is big enough for the switch to poke through.
6. it can be a tight fit, but I filed away, both the hole and the insides of the spacer until it fit. Use the exacto knife/razor blade tool to cut away the plastic trimmings if needed.
7. insert the switch and screw into place.
8. now find your hood pull and follow it to the rubber grommet that goes through the firewall. Take a hanger (unbend and cut off each end where the curly things are to make it smooth) and tape your power wire to the hanger so you can push it through. Better tape that baby good. Not too thick though, but enough to ensure it won't come apart. Mine did, so the 2nd time I taped it up even better.
9. Starting in the cabin, push the hanger through (following the hood pull cable) the rubber grommet - no need to cut, it will poke through just fine if you stay close to the hood pull cable. You might have to bend the hanger a bit so you can find it and pull it out from under your hood.
10. Once you pull the hanger through, just cut the wire (no need to fool with the tape mess).
11. Now just run the wire to your battery and then zip tie the wire into place. I went around my air filter, and across the front of the truck (basically following the hood pull cable), to the battery. Attach the power wire to the battery.
12. Now just run your ground wire to the switch, and your acc wire to the switch, reinstall the panels and you are good to go.
In the images, you can see the zip ties. To show you how I ran the wire, I started on the driver side by the air filter, and worked my way around the front of my truck to the battery on the passenger side. Look for the white zip ties to get an idea of where I secured them into place. (NOTE: you don't need to jack your ride up, I just thought this was a good tip if you don't have one - be sure to set the parking break and rock your truck to test and make sure it doesn't roll down on you before getting under!)