Clips can be loaded into TouchViZ sets from three sources, the application's documents folder and the iPad's media library and camera roll.
To transfer clips from your computer to TouchViZ's documents folder on the iPad you use iTunes File Sharing:
Using the same method you can also transfer touchviz files of saved sets to and from your computer for backup or to transfer them to another iPad. Please note that media loaded into TouchViZ from the iPad's library is not portable across devices.
Here's Apple's guide to syncing videos to your iPad library: