Use My Files to find the video and tap it. Your default video player will play it. (If you don't have one, look in Play for video player and install one. Then tap the video file again and you'll be asked whether to run that app just once or always. Run it once, just to see if you like it - what you can do with it, where the controls are, etc. If you do, run the video file again, and say Always. If not, uninstall it and try a different one. (I use VLC - it plays just about anything.)