Custom child theme

I have Installed WP 4.2.2 , I have followed the instructions here by downloading the child_theme files using the download button down at the page.

https://wpsites.net/wordpress-themes/how-to-make-your-own-child-theme-for-wordpress-beginners-guide/

I`m currently using the sweet twenty sixteen theme.

But I have not written any code except from what already are in these files. I expected, when using this theme , that the page would be blank, but thats not the case. I hadnt expected that there was a header field either..
https://test.nygards.no/new-theme/

I have also downloaded a Multiple Theme add-on : jonradio Multiple Themes

Without any luck to create a blank page (Which of course is not the ultimate goal)

So my question is, how can I for example get a white backgrouund, how can I add add-ons to this page, and make sure that addons from sixteen twenty theme is not shown on this page