Hi Cuyahoga County, At this point with the seedlings starting to germinate and send up shoots, you will have to keep them from freezing over the winter.  That can be accomplished by putting them in a cold frame or other enclosed area and mulching them in.  I would use a fine mulch that can let rain down through but not suffocate the plants. 

I thought a lot about this question over the weekend.  I raised a lot of oaks for the city for planting out.  The problem with that is that squirells love them as well.  All the pots had to be enclosed in a cage with hardware cloth (1/4 inch) to keep them from tearing up the pots and eating all the acorns.  That would not be too true with apple seeds but I would still enclose them in a cage of some kind to keep animals (chipmunks, too) from rooting around in there and ruining the germinating seeds.  
The other problem is that you won't get any apple tree that resembles the one you picked out the seed.  You can go to a place that squeezes apple cider and save the seeds and dry them out and then plant them.  You will get a lot of apple seedlings.  Then you take grafting classes and learn how to graft the desirable apple to the apple rootstock.  It takes some skill that can be learned and practiced.  That is the way they get new apple trees in the trade except they use a specific rootstock that will dwarf the tree to keep it to the desired size.  
So, to sum up, I would find an enclosure with an open bottom, put the pots in there, keep them watered through the fall, cover with loose mulch and nail on a hardware cloth cover and let them germinate over the winter.  Hope this helps you.  Don