You can get rid of a couch by hiring a junk removal pro who can get it safely out of your house and dispose of it. There are other options as well, including renting a trailer and hauling it to a proper disposal facility, or leaving it out for someone to pick up.
However, a junk removal service is the easiest option. This keeps you from having to lift a heavy object or risk scuffing up your walls. Furthermore, a licensed junk removal service can responsibly dispose of a couch, saving you from having to find a site.