To change the backgrounds without css, take a look at your WordPress admin, and look for “Customizer” under the “Appearance” tab/link. Then click “Background Images” and you can see the sections where you can add your images.
For the Parallax code, take a look at this recent comment of mine – https://appfinite.com/topic/parallax-feature-option-activation/#post-11937
The documentation will show up in a different area as soon as I get it done, but the original docs can be found in the Yellow Sticky Posts at the top of the Epik forum – https://appfinite.com/forum/epik-theme-support/ From there you can see all of the code snippets/tutorials that explain how code was added in certain places.