Why has my inner tube enlarged after moving from bicycle to repair
You can just stuff it into the tire. It will be fine. 


Get one of the tire's beads on the rim.
Put a little air in the tube so it holds its shape.
Put the tube's valve through the valve hole and work the rest of the tube inside the tire.
Work the other bead onto the rim. As you get close to the end, you may need to deflate the tube. Make sure none of the tube is pinched between the tire and rim.