I know nothing about Orbiter but I feel that it is time that I ventured into it's rather inviting world, any chance that someone could give me a step by step guide on how to install both the base program and the Apollo mission addon (and since there is two, what is the best?)

I have been looking around and I can't seem to find a step by step that I can wrap my head around, perhaps someone here can just list the steps in plain english

Thanks so much in advance.