Movie Maker App for Windows 8.1 Smartphones FREE

Movie Maker for the Windows 8.1 phone helps you quickly and easily combine videos, photos, music and even cinemagraphs into movies for sharing anywhere. In four steps you select your footage, select a theme (that's a style for your movie), add music and titles and then you're ready to watch your movie.

Here is a review from PC Magazine that rated the app as excellent and a link to the Movie Maker website with simple tutorials.