Engined gets installed just like any other theme :
- Download the theme zipped file from the Engined child theme page and save it anywhere in your computer.
- From your WordPress Admin area go to Themes > Add New.
- Once on the Add Themes page, upload the Engined file to install it.
- Activate Engined.
Of course, Divi needs to be present in your site, since Engined is a child theme of Divi.