Sorry I don't have rescue Your Videotapes to give a more specific answer, but suggest you start with 'Help' from the top menu line. Magix are not know for their excellence of documentation, but I'm confident a search for 'cut' 'delete' etc will find you something.
Just looking at the Rescue site ( http://www.magix.com/us/rescue-your-videotapes/detail/ ) I see a little icon between the video transport controls and the timer that looks very much like a pair of scissors cutting a scene in half.. Have you tried that? Editing is 'non-destructive' so if you cut or delete something your are only removing it from your project list -- the original captured video files remain unchanged. And of course you can un-do with [Ctrl] + [Z] like any other Windows program.