I can see that the actual video to be used is in the VideoBackground/video path....
To "Install" a different video, my guess would be you simply change the sample "video" file to one of your own, but with the caution made by Arsalan above to be noted.
there are no options to "add" a video but by manually adding it, I suppose.
As the landing screen would be for all to see as well as could well be an "intro" video for some time to peak the interest of potential users, having an option to "install" videos at will would defeat the purpose, I have tested it on desktop machines and ipad (at 1024 but not working at 768px), but having issues with mobile use for obvious screen size problems below 1000px, as already indicated..
However, you should also look at the necessity to have a video at the lower resolutions whilst also trying to display the "Login" or "Create an Account" information on a mobile device....I feel, although it would be nice to have at the lower resolutions, a thought has to be put on the practicality of trying to fit all the information on smaller screens.........Just my view