You should have a working CVS installation on your system, and you should be able to execute CVS commands from your Operating System Command Line. Although SNiFF+ helps you performing CVS commands, you should know the CVS concept and how to operate the CVS system from the command line as well.
Note that this paper does not replace an introduction on CVS. For background information, please refer to the resources listed below.
You should also be familiar with the SNiFF+ Project and Working Environment concepts.