Remove the wiper arm by removing the plastic cover over the mounting nut on the outside of the rear window, remove the mounting nut for the wiper arm. Be very careful to not crack the window. You may need to use a small puller to do this .
Remove the plastic housing on the inside of the rear window. Remove the 2 nuts holding the motor assembly to the window. Remove the entire motor assembly, disconnecting the wiring harness.
Reassemble in reverse order with the new motor assembly.
You can also GOOGLE for a pictorial instruction write-up for the procedure.