The sixth generation Civic is unusual in that the main relay is located on the passenger side of the dashboard, so I've written a separate how-to just covering the differences. Refer back to the Main Relay Kill for more information.
These are the tools and supplies I used during this project. Refer to the Main Relay Kill page if it's unclear what any of them are.
Remove the two screws holding the hinges of the glovebox and pull it out carefully.
Now remove the dash corner and side trim pieces so you can access the main relay.
The main relay comes out with a single 10mm bolt.
Push the tabs in to remove this pop tab that secures the wire loom.
Now pry up this wire pin retainer so you can de-pin the black wire.
If you look inside the harness, there's a little tab putting pressure on the pin to retain it. A very small flat blade screwdriver can be used to push the tab down while you push the pin inward so that it doesn't catch on it, then pull it out of the harness.
Now I insert a ground wire I got from a main relay at the junkyard. Some have one single black wire and some have two.
Cut the electric tape at the end of the loom to access the wires. You will be tucking the factory pin into the loom and running the new wire as if it were the original.
Now extend the newly pinned wire with solder and heat shrink. Re-tape the end to secure the loom to the wires.
Now you run the extended wire to one of the pins on your switch. The other pin on your switch goes to a ring terminal to chassis ground.