You mean a bulb with several cloves I assume? Plant it right away. Separate all the cloves. Plant with the point up (the same direction they were in the bulb--there's a wee woody bit at the bottom where the roots will grow) about 4-6 inches deep and put some mulch over top. (A 4-inch layer of hay, for instance)
If the variety is not suited to your climate, it may not survive. But if it is local, it should be okay.
I might be missing something here because I live in a much warmer area and so there is no threat from cold that is severe enough to get the garlic.
Cold does not pose much danger to garlic. There is still some danger... I don't remember what exactly. I think you want to make sure the garlic doesn't freeze before the green tips have started coming out, but even if it does it's usually fine. IIRC. But mulching will prevent any real problems.
If you're in a warm climate you don't need the mulch really.
Here, we get plenty of freezing temps but the ground doesn't freeze solid--there are always many thaws through the winter. We can plant garlic in the middle of winter and it is fine and the mulching isn't for cold protection.
In CT you probably have deeper cold. Frost heaving is a possible problem--I think the mulch helps with that?
Anyhow, I thought that the California-type garlics were a lot less hardy