near the top of the screen there's a "make movie" button. Hit this and follow the instructions. Your completed movie is just a series of instructions for VMS to folow when it does the make movie task. Once the movie is made, you'll be offered the opportunity to view it on Windows Media Studio
Microsoft Lumia 950 vs Lumia 950 XL: What's the difference between Lumia 950 & 950 XL?