1) From the edit screen tap on 'Export' in the top right corner of this screen.

2) This Export screen will show up.

3) Tap on video to export the video as an mp4 Video. 

Note: If your design has premium elements, and you are not premium, you can still export your video design as Draft (with a watermark). If you wish to export the video, you need to purchase premium or purchase a one time pass to remove watermark.

4) The following loading screen will show up. Rendering a video is a very intensive process so it might take a few seconds or even a minute to render a video. The longer a video is the more time it will take to render. The number of element in a video design also effect the rendering duration.

4) When export is finished, find your exported mp4 video in your phone's gallery.