Answer: It is important to keep the soil slightly moist any time it is not frozen. You will need to dig into the soil with your finger and see if it is still damp so you know when you need to water.
You should try to insulate the roots. You can do this by double potting it with insulating material between the containers, by wrapping the pot in burlap and stuffing that with dry straw or dry oak leaves for example, or by heaping mulch over and around the container (not over top of the tree itself.) Whichever of the above you try, also mulch over top of the soil.
Provide wind protection. This is very important as it helps prevent it from drying out.
If possible, to minimize the effects of freezing and thawing and heat/sun reflecting unnaturally off the building, it is better if you can set it on the north side of the building, or somewhere that it receives minimal direct sun. That will help keep it at a more even temperature.
If you need to repot, wait until spring to do that. Please understand that overwintering an evergreen in a container under home conditions is usually stressful on the plant, it is not an easy thing to do well. Good luck with your tree!
Q&A Library Searching Tips