First, what you downloaded is a scam version of Movie Maker. It probably asks for you to pay a "registration" fee to be able to save your movies. Another clue that it is a scam version is that it shows the version as 2016 while the official version only got updates to 2012.
- Where to get a Safe Download of Movie Maker
- Scam version of Windows Movie Maker appearing at top of search results
Second, let's clarify where you are trying to change the background color. I suspect you have added a photo or video into your project and because it is smaller than the aspect ratio of your project (probably 16:9), you are seeing a black background. It sounds like you are hoping there is a way to change the background color from black to a different color. But that's not a feature that is present in Movie Maker.
The background color in Movie Maker only applies when you make a full screen title with a background. For example, if you click on the 'Title' button on the Home tab, you get a full screen title with a black background. You can then change the background color from two places:
- Video Tools > Edit - Background color
- Text Tools > Format - Background color
Either place does the same thing and it changes the background color behind the text. The option only gets enabled when you have selected a text title from your project area.
That option changes the whole background behind all the text. If on the other hand you are looking to have a colored box behind each line of text, that isn't possible either. What you *can* do assuming you have the official version of Movie Maker 2012 is change the text *outline*.
I really don't know why Microsoft never added the ability to change the background color behind a photo or video, but if that's what you are trying to do, it's not possible inside of Movie Maker. One thing you could do, is to manually edit each of the photos and put them on a 1920 x 1080 background in the desired color. Or you can crop your photos so they are all in a 16:9 ratio and don't show any background anyway.
tl;dr - You can only change the background color behind a text title, not a photo or video.