Help files for VidSync are online on the VidSync website/wiki, including a "how-to" video tutorial screencast to help new users get started.
A peer-reviewed paper describing the mathematical methods underlying VidSync and testing their accuracy is cited below. If you don't have access behind the journal's paywall, you can download the accepted manuscript for free. It's identical to the published version except for formatting.
Neuswanger, Jason R., Wipfli, Mark S., Rosenberger, Amanda E., and Hughes, Nicholas F. 2016. Measuring fish and their physical habitats: Versatile 2-D and 3-D video techniques with user-friendly software. Canadian Journal of Fisheries and Aquatic Sciences 73(12): 1861-1873.