Beginner seeks help downgrading from Mountain Lion to Snow Leopard

Hi,

I'm a complete beginner with all of this so I wanted to find out whether someone could please explain to me in a simple language how to downgrade from Mountain Lion to Snow Leopard. For some stupid reason I upgraded it last week ago and now am having horrible regrets. I tried searching for answers from people who had the same inquiry, but it's too complicated and very specific to their exact situation and setup. Plus, I don't understand – is there more than one way to do it? The USB or Wi Fi way... huh?

There's also the fact that my disc drive doesn't work, nor do I have an external one, so if there's a step that requires me to insert a CD, I won't be able to get anything done. I would be more than okay to simply restore everything to the factory settings if it came down to it, but if I understand correctly, it's not at all what it sounds like and requires you to install one of the OS X's afterwards anyway? Or no? I don't get it!!

Anyway, I do have a virtual copy of Snow Leopard if it helps.

Please, someone assist this silly person!