The -C parameter specifies to use compression. The 5902:127.0.0.1:5901 part maps your local host 127.0.0.1 port to your remote machine. The rest I think is obvious. Once that is done, all you have to do is run the tightvnc client poniting it to your local host's 02 port, like this:
That should give you a fast, encrypted connection to your remote machine using plain ssh and vnc. Try it.