[Sugarcube] Implementing Background Video

Hi everyone,

I'm using SugarCube 1.0.34 and I'd like to have an awesome background Youtube video. I've seen some thread about it but I really can't make anything work.

Can someone please give me a clear and fonctional step-by-step tutorial that would state exactly where do each group of code lines go (stylesheet ; passage), where to put URL and so on?

Thanks my dear twine comrades