Congrats! 120 film doesn't have a canister like 35mm film, as you know, so you must wind it to the end to get it off the spool. The spool you wind it off of becomes the take-up spool for your next roll. You don't need complete darkness to remove the film but I wouldn't do it in direct sunlight either. Shade is good. Once you've removed the spool from the back, you'll find a little tab on the end of the rool you can fold under, and a strip of paper around the middle that you can lick and stick down to keep the film coiled around the spool. Depending on how long you're going to keep the film before processing, I usually wrap them in aluminum foil and keep them in the fridge (short-term) or freezer (long-term). With summer temperatures bouncing up around the northern hempisphere, keep in mind that if film gets too hot the emulsion can separate from the backing. Don't keep it in the glove box or the trunk of your car...
Mike.