To initially checkout a copy of plex86 from the CVS repository.   Note that the use of -z3 (use gzip compression during transmission) is optional.

cvs -d:pserver:anonymous@cvs.sourceforge.net:/cvsroot/plex86 -z3 co plex86

To update your local copy of plex86 with modifications which developers have made, change directory into the main plex86 directory and:

cvs -z3 update -Pd
For more information on usage of CVS, check out the CVS documentation at SourceForge.   Look under SF.net Resources -> Site Docs.