Get the correct wiring harness adapter from Metra or other (similar)

Just do a little research to get the right one

With some of these, you have to change the pins for the Red and yellow wire

you attach the Kenwood wire harness to this adapter and then you plug this into the factory harness

solder all connections and deal with heat shrink or tape

Unless you enjoy doing things twice, DO NOT use crimp butt connectors