The Backglass GI connection comes from the J14 header, located in the upper-right corner of the AFMr Kit. The wires are mainly green, and purple.
This is what the "light tub" wiring looks like for the Backbox General Illumination (GI) upgrades. There is one Purple General Illumination (GI) connection, and (surprise!) two Green GI connections. The main Green GI connection is closest to the Purple GI connection (middle of the pic). The other Green GI connection is usually nearby (approx 2 inches), but sometimes there are games where the second Green GI connection is further away. Again, I do not know why there are variations, but if your game has the two Green GI connections located further than 2 inches apart, send me the distance between the two connections, and I'll send you a proper cord.
Chapter 1: Tools and preparation
Chapter 2: Mounting the board(s) and connecting power
Chapter 3: Inserting LEDs in the Mini-Saucers
Chapter 4: Installing the mini-saucers back in the game
Chapter 5: Setting up the Hallway LEDs
Chapter 6: Running wiring harnesses under the playfield
Chapter 7: Connecting the Backglass GI
Chapter 8: Testing and jumper settings
Chapter 9: Troubleshooting