Here's the easy way. Look next to the oil filter housing and you'll see a large rubber grommet. If you're unsure of the one I'm talking about, it's the one with two yellow lines going through it. Only one grommet has two yellow lines, I can assure you this!

Next, pop off the 3 small covers on the underdash panel on the driver's side, and remove the screws. Pull the panel down. Here's where it gets tricky. Slide the driver's seat all the way back so you have more room to work. Locate the backside of the grommet with the two yellow lines. This may take a while, and you REALLY need to stick your head under that dash! Once you have located that, go to the other side (engine side) of the grommet and pull off one of the tabs, This will expose a hole. Make sure that the tab you choose to pull off (there are several) will make a good seal with the wire that you will thread through this hole. It's relatively easy after this, because you can see light shining through the hole.