Taillights and dash lights keep going out after multiple fuse replacements

Hi there. A few months ago, my friend installed an aftermarket stereo into my car after my original radio got wet and eventually stopped working. A couple months after the install my parking gauge letters that light up at night went out and now as of recently by 10a TAIL fuse keeps blowing out which causes my dash lights and taillights to go completely black which is especially dangerous at night and when I put in a new fuse it lasts maybe an hour or two max. How do I fix this? I don’t know the first thing about what to look for in wires and how to fix wiring in a car!