Some people say they can do it in 15 or 20 minutes, but it always takes me at least an hour!
First, I prop up the back of the snowthrower such that the pins in the back of the snowthrower line up with the slots in the lower front of the tractor frame. (The spring pins in the top rear of the snowthrower frame have to be pulled to the "out" position and then locked.) Then I gently drive the tractor up to engage the pins. I do this **dismounted from the tractor**, on the right side. No doubt this is a no-no, but otherwise I can't see what I'm doing. Takes several back-and-forth maneuvers of the tractor to get the tractor frame to go just inside the snowthrower frame. Once the tractor is moved up onto the snowthrower, I then have to knock out the supports holding up the rear of the snowthrower, so that the snowthrower pins can settle down into the bottom of the slots in the tractor frame. Then the whole snowthrower has to be pivoted up and to the rear, so that the top spring pins can be released into the holes in the tractor frame. (When I do this, the snowthrower pins often come out of the slots, so I have to start over!) But anyway, I eventually get the pins in the slots and the spring pins into their holes. Then the drive belt has to be maneuvered onto the upper and lower pulleys - best done with the tractor grille removed.
I suppose it would be a lot quicker and easier, if I had two strapping young relatives, to just pick up the snowthrower and push it onto the tractor. But I don't !!