Installation of dependences

I need some feedback/help on how to install the dependences on Pressbooks, because it is not clear for me at all from the readme file.

Which dependencies are you referring to? Prince/KindleGen/EpubCheck etc.?

Yes, for these dependences but more specifically for the EpubCheck one. We need to install it in order to test the bug @colomet told me about the Ebook settings.

Did you visit the link and read their documentation?