Mod to 2nd Gen engine bay fuse box to tap ignition only wire?

I’ve seen a mod posted somewhere on how to access or modify the 3rd Gen engine bay fuse boxes to wire in an add a fuse or tap into an ignition only fuse. I have a 2nd Gen and haven’t seen one of these mod write ups or don’t know enough wiring jargon about what to “google” or search in order to post results. Does anyone have a link to one of these posts or info?
I have a trigger 4 plus system to wire in accessories and want to wire it to an ignition fuse rather than being wired to my battery full time as it is now. Thanks. Sorry if not clear what I’m asking. I don’t know the words to say what I’m trying to convey. Hopefully others do

 

Do you really want a ignition Fuse or do you want switched power meaning the circuit is only energized when the ignition switch is on?

How much current does this need to handle??

Do you have any schematics with this device telling you how to wire things??

 

I’ll tap whatever I just want it to be controlled with something ignition based vs just an always live switch. But the main thing I wanna know is how to get I to the fuse box without having to like leave the top off. There was some workaround way folks got through it on the 3rd gens to route like add a fuses

 

Don’t have to leave the top off. Route wires from the bottom where there’s existing wires passing through.