who are you sshing to? the proxy server?

generally its pretty straightforward and i may misunderstand what you are asking, but on linux the command is:
Code:
ssh -L localport:server-tunneling-to:remoteport ssh-server
where ssh-server is the ip of the server you want to ssh to (i think your public proxy), server-tunneling-to is the ip of the server you're tunneling to (your public proxy again?) and local port is the port you want to connect your browser or w/e application onto the tunnel, remote port is the tunnel they want you to connect to

on windows use putty and its under ssh tunnels, same stuff is required

hopefully thats what you want

a way i commonly use ssh tunnels is like this

ssh -l myusername -L 10000:blocked.domain:80 my.home.server

then i go to localhost:10000 in firefox and i have blocked.domain

hopefully that helps