FYI - While browsing on Amazon today I noticed a book on using Sigil. It seems to have just been released a few days ago.
How to Create and Format EPUB eBooks Using SIGIL (v 0.7.1)
http://www.amazon.com/Create-Format-.../dp/B00BXJAUQ6
I'm not associated with the book or even know whom the author is, nor have I read it and am not recommending it. Just thought people here might find it to be of interest. Most people on this forum probably don't need any instructions.