@Tulpana
If you are preparing your book in Word, I strongly recommend to any non-html user or html newbie that is confused about how to create an inline TOC to get the free Kindle book by Mark Coker of Smashwords,
http://www.amazon.com/Smashwords-Sty.../dp/B004XWJ7UK .
Specifically, use the tutorial in "STEP 20b" to create an inline linked TOC in MSWORD before importing to Sigil; it is both easy to understand and essentially bulletproof.