Antique Automobile AM-FM radio install help needed

[CS1972]

My Antique Automobile AM-FM Radio arrived a week ago and I removed everything I needed to today in order to install the new radio and speaker. What I have left is 3 wires: one appears to be the factory Red wire (I’ll refer to as R6) which was plugged into the fuse block labeled “Radio”, the second red wire (I’ll refer to as R5) also goes to the fuse block (without connecting to anything else) but it is “jammed in” with the fuse labeled “Tail stop” (see pic) and lastly a black ground wire. I know that second red wire (R5) shouldn’t be jammed in with the fuse and plan to remove it.

Based on the new radio instructions, R6 is the main power input and connects to the Red fused wire on their harness, got it. But then the new radio instructions says: “There is a green wire that is used for the dial light and should be wired to the dash light circuit ahead of the dimmer rheostat so that the radio lights come on when the other gauge lights are turned on”. So this is where I need help, where do I need to plug in and/or connect to an existing wire to make this work? Wiring is not my specialty, so be gentle.