on/off switch

Hello, So I'm a first-time user here and I own a 1963 Nova with pretty much original everything INCLUDING the fact that the original owner ordered it WITHOUT a radio (so there is a rare factory-installed delete plate where the radio should be). I'm in the process of installing an amp either...

I am thinking about putting in a mono amp and a subwoofer and I was wondering if it i possible to hook up an on/off switch for the amp just in case I don't want a bass overload for some songs. I have looked around and I have seen some people mention but I am just wondering how exactly to do it...