Seriously, you don't need a youtube video to explain how to replace a light switch. A screwdriver and a decent amount of curiosity will get you a long way.
Well, I mean it's probably good to watch the YouTube video anyway in case you don't know about turning off the fuse box. Might seem obvious in that case, but when you're just learning something you don't know what you don't know yet. Good to at least find out if there's anything that might kill you.
Plus knowing where the fuse box is, of course...