In the large container you are using for the brine, add in the water, brown sugar, and kosher salt. Stir until dissolved.
Prepare turkey by taking off all of the packaging and removing the innerds. Rinse off the turkey and then submerge into the water, sugar, salt mixture.
Sanitize every surface that was touched by the turkey or turkey juices befoer moving onto adding in the rest of the ingredients.
Cut the oranges, lemons, and onion into quarters and add to the water mixture. Add in the bay leaves and the peppercorns. Place foil or plastic wrap over the top of the container with the turkey. Place in the refrigerator for no less than 24 hours and no more than 3 days. The longer the turkey stays in the brine the more the proteins break down, any longer than 3 days and the meat will begin to dissolve while it cooks.
Once the turkey is in the finished brine and sitting in the refrigerator you don't have to do anything with it until you want to cook it. Let it just sit and flavor for a couple of days.