I've been using YouTube's Video Editor. It wasn't pretty but it did the job.
Up until September 20, 2017 when YouTube killed it with no explanation.
I needed something else simple.
Windows 10 Fall Creators Update (1709) included a new Photos store app.
It doesn't have the most intuitive interface but it's way better than YouTube's Video Editor.
Here's an example of a video I made with it.
Windows Central has a nice article on it.