Hello Nikos,

You can find the documentation in the main archive or online:

http://clapat.ro/themes/satelite/documentation/

However, regarding changing fonts:

Although we do not recommend changing the fonts (because you may need to do a lot of collateral changes - margins, paddings etc) you can use plugin such Easy Google Fonts 

https://wordpress.org/plugins/easy-google-fonts/

or

https://wordpress.org/plugins/use-any-font/

or for custom fonts

How can I add my own custom icons/fonts to the theme?

You can do also a sweep through the CSS files (style.css and files from the /css folder) and repace the font-family attribute