New Idea....New Drafts

So, I had this dream and I woke up thinking - that would make a good story.  Most of the creative writing courses/support/advice say this is a big NO NO as the dream is usually unworkable nonsense. I'm ignoring that little voice of doubt, instead I'm hammering and chipping away at the idea to make it into a manageable plot before I start drafting. I've never done it this way round before, but I'm determined to have a believable and workable plot line in place FIRST. This is in the hope that I when I come to the editing it won't mean a massive overhaul on the structure. (This is all just theory you understand and like everything else I'm making it up as I go along - but I'll keep you posted....working title for it is: TIME TRAP)
The other thing to tell you all is that following advice from a fellow writer I'm trying out Scrivener. Oh Lordy - it's a little bit complicated, but I'm hoping that it will get easier. Keep thinking I've lost all my text and can't get my head round 'The Inspector'. Tutorials are so wordy. I've got a 30 day trial to make Scrivener my friend.