Create different backgrounds for different pages on my website

This is very simple, I just need you to put different background images in different pages, then tell me where you did it (which file and location in file) and I will take it from there. You don't need to care about what images you are putting, my problem is that I cannot create independent backgrounds for different pages, backgrounds are all connected to 1. This is a very simple project for someone who knows about coding. Please bid only if you understand what I'm asking here.