How to use video files instead of camera streams

Hi, this is a great piece of software. Reading the final report on this project it sounds in item 4.2.7 that it is possible to use pre-recorded video files instead of live camera streams. Is this true and if so, how can I make it work? - I am not a computer specialist, so if it is not easily possible then it may not be for me. 
Thanks for your help
Thomas
