You can find this product under Honda FIT LED Rear Pillar Lights (72-001).
This is the rear bulb-less side pillar reflectors you will be replacing:
Step 1: There are two bolts you need to remove before you can take off the rear side pillar reflectors. You can then proceed to remove the rear side pillar reflectors on the rear windshield.
Step 2: This depends on the production of your Honda FIT, but some have a push tab that you need to push for lock-in. For any Honda FIT without the hole for this push tab, you can just remove it with a wrench.
Step 3: Install back the LED rear pillar lights.
Step 4: Extend the given wires to the existing harness: black to ground, red to tail light, white to brake light.
Afterwards, this rear side pillar reflector becomes an LED tail light with the same style as your existing one.
Test to make sure everything works. Enjoy your Honda FIT LED Rear Pillar Lights!