If you are cooking them now, put them into the oven at 350 degrees for 8-10 minutes.
If you are freezing them like I do, place them on a baking sheet & freeze until firm. Then pop them into freezer bags. I like to wrap them with aluminum foil before putting them in the freezer bags - just to be double sure no nasty freezer burn hits them. From frozen, cook at 375 for 20 minutes.
Lay all the bagel halves out. Combine the shredded cheese, chopped pepperoni, & pizza sauce. Spoon a couple tablespoons onto each bagel half.