Bob's your uncle!

Bob's your uncle - something that you say after you have explained how to do something,  to emphasize that it will be simple and successful.

Example - "You simply put on the stain remover, leave it for an hour and Bob's your uncle, the stain's gone."

Image - http://lib.store.yahoo.net/lib/organizeeverything1/BannersBobsYourUncle.jpg