You didn't mention if you have a classic (real) Mini or a BMW- made MINI. The solutions you get will be vastly different.

On a classic Mini, only some of the fuses in the fusebox are continuously powered. (Brown wires are always powered.) Any other inline fuses should be left alone as they are likely sized for what they serve. The fuses that are not continuously powered are fed through the ignition switch, but it and the wiring from it are probably not sturdy enough to power an amplifier. The answer is to power the amplifier from a hot (battery) source, through a fuse and then through a relay controlled by a wire from one of the circuits controlled by the ignition switch.

I'll second that. Any amp worth running (i.e. more powerful than the head unit/radio ) draws too much power to safely share with another circuit. (i.e. not many circuits have so much excess rating that you can safely draw the power to run an amp.) 

Any worthwhile amp should be given its own power feed and fuse.

Hummmm

If he’s trying to hook up an amp, in-line fuse off of the battery And then remote wire for amp hooks up to the radio remote wire to turn it on and off

Not sure what the problem is

My husband did car stereos and tint for 20 something yrs and my mini has him stumped.  He's been looking for a fuse for the amp that isn't hot when car is off so that the amp doesn't have power 24x7. All fuses have power when car is off. Does anyone know a location to hook the amp into?