[Doitsu]

Originally Posted by Koboder

I am writing my first e-book. I'm using Sigil.

FYI: If you've created an epub2 book, you'll need to convert it to an epub3 book with the ePub3-itizer plugin. Otherwise you won't be able to use epub:type attributes.

Shameless plug: since this is your first book, you also might want to install my EPUBCheck plugin and check your book for errors.
(If EPUBCheck reports any error messages that you don't understand, please ask about them in the EPUB forum.)