Move everything out of the pathway you'll be rolling the couch past. Pick up any area rugs as well as furniture.
Place the dolly close to the couch. Have your helper lift one end of the couch. Roll the dolly under the couch and position it in the center to properly balance and lift the couch.
Carefully and slowly push the couch from one end rolling it over the floor to its new place. Don't push too fast or the couch may rock off the dolly or damage a wall by sliding into it.