connect to rtrorrent through command line

I've been using rtorrent through web interface but l would like to try managing it through command line.

My question is, how do I access/connect to already running instance of rtorrent? I really don't want to accidentally start another instance of rtorrent, I believe that's a big no-no :)

I understand the part about connecting through SSH. I'm in, at the command line prompt. Now what?