From my experience, I have found no way do create popup images. I used the software for a long time before I upgraded to a better alternative and I found no way to do any simple but necessary edits. I would recommend moving to a different free software with multi-track editing capabilities in order to get better results. A friend of mine used VSDC and it seemed to work pretty well for him. Not only that, but it has multi-track editing so you can do all the stuff you'd want to. Keep in mind sticking with Movie Maker isn't bad, but I would recommend the upgrade
Happy editing!
Edit: Apparently HitFilm is also a good alternative! Just keep checking things out to see what works best for you.