Congrats on your new "toy".
Here's our time progression that you may well end up following:
Winter 1. Carefully store our Branson in a "portable garage" just like yours all winter
Winter 2. Occasionally get lazy and leave Branson out, with a lovingly attached ATV cover over the cockpit area
Winter 3. Leave the Branson out most of the winter, covering the cockpit with a bungeed tarp
Winter 4. Always leave the Branson out, with a tarp sorta held in place with decrepit bungees, since the "garage" is too full of other crap
BTW, if you're going to be using the tractor outside in the winter, especially if you have any slopey areas, I'd suggest you find some tire chains, at least for the rears. Up here in Eastern Ontario, I find it's fine without in the 1st part of the winter, but it gets really slidy on R4 tires when you have icy packed snow on (semi)cleared driveways, and of course when there's any freezing rain or you get into the spring freeze-thaw cycle. We didn't have any for Winters 1 and 2, and it really limited in what conditions we could actually use the tractor meaningfully. Even though we're ony 45 mins from you, you're on much flatter ground, so you may fare better than we did, but I'd still think about it.