After market radio wireing

I am installing an after market radio, with an wireing harness adaptor. What is the best way to run the harness from the radio to the back area where the reciver was replaced? It is on a 1994 convertible

When I did my '96 I removed both sill plates because I was also replacing speakers and speaker wiring. I ran the "adapter harness" under the carpet next to the sill plate and tie wrapped it to the existing OEM harness which was already there.