Hello there!
Make sure the coop is well ventilated but not drafty. Coop is dry, make sure they have dry, soft bedding (what type do you use?)
Keep their water unfrozen, I recommend a heated waterer. I assume you don't have a run (a pen)? If not, make sure you get some things to keep them entertained and keep them from getting bored out of their minds and being aggressive with each other.
You can hang a head of lettuce or cabbage and let them peck at it, give them treats, and you can even buy "chicken toys"

Just search google and you'll find it.
If you do have a run, cover it with plastic or a tarp to keep the snow out.
Its the chickens choice to come out or not, some chickens don't mind the snow on their feet (you can throw straw on the ground to help with the cold). Some of my chickens have to be forced out of the bitter chill and snow, but some of my other chickens prefer to stay in the coop where its warm.
If you have any other questions, don't hesitate to ask! Best wishes!
