[djg]

You need get to the wiring harness connector behind the trim, near rear seatbelt upper anchorage, splice the red sensor lead into the brown harness wire using a connector as shown (All Auto shops have them).
You can connect the black to a earth bolt you will find behind the trim.

For full details see the .PDF file how to fit HONDA OEM Sensors.

You do need to remove a lot of trim, you have to be quite forceful in "pulling" it off, but it all goes back OK. Sorry no pictures, it was getting late when I finished the job one evening, and its all back together now.

Good Luck.