I notice that you live in zone 4 or 5. I live in zone 5, so we have somewhat the same climate. One way to begin would be to wait till November, or later, when the leaves are off your wisteria. Then you can see what the main structure is. You could begin by pruning lots of the lower side vines and begin to create a lower trunk of sorts. That way next Spring it won't be so out of control, but you will not have pruned off too much and you'll still get blooms. This would be a time also (late Fall) to place some kind of support on it so it can begin to be a climbing wisteria.

If you have the room to let it ramble you could actually leave it as a sprawl.

I've seen one in a local front yard that does just this. It looks like some sort of draped dragon and it is glorious in both spring and autumn.

The new sprouts are kept under control and the trunk/stem has been allowed to thicken into a lovely framework without a lot of cluttering.

It measures about 20'x10' and has been there for many years. It's probably a Japanese Wisteria.