Hi Christine,
Well, as you've probably guessed, it's best as a two person job, with a possible third helper to lift the bendy section up!
I fit the wooden sides to the bendy section first, on the ground, and the wooden hinge supports underneath at each end, with the brass hinges fitted.
Then fit the end pieces, with middle hinges, to the main roof using half a dozen screws across the bottom hinge and keep them vertical by clamping some 2x1 timber vertically (with windows removed) across the central hinge to stop them folding, and then clamp the end sections to the wooden curved roof supports, with packing pieces in between to keep them vertical - sounds complicated but if you try it you'll see what I mean, I hope
Next, with someone standing in the vehicle, we slide the bendy section up so it lays over the end sections.
You might want to use 2/3 lengths of planed timber to slide the bendy section up on.
You then need someone outside with some strength and stamina! on a stepladder to pull down one of the wooden sides and push it down and in towards the hinge so you can fit a few screws. Make sure you fit several at each end before your helper releases the pressure as there's a lot of strain on the ends on the hinges!
Once you have say 15-20 screws in the side, it's time to see how accurate your measurements were!
Get your helper to try to pull down the other side - it's hard work to get it really tight - to see how it fits.
You probably won't get it all the way down, but it should give you an idea if something's not right.
As the roof is under a fair bit of tension at the ends, caused by the end panels, I usually then lower the end panels and use a length of timber, around 5'6" long or so, vertically in the centre to hold the roof up, with a length of 4"x1" or so horizontally between the vertical timber and the roof.
That makes it fairly easy then for your helper to push the other side down to the hinge for you to fit some screws, again about 20 or so with most at the ends.
Then, carefully try to lift and unfold one end panel.
If all goes well, and your measurements were exact, the end panel should be a tight fit.
However, each one I've done needed adjustment!
If you can't get the end panel vertical, you need to remove it, take the centre hinge out and cut/plane the top of the bottom section and the bottom of the top section equally.
If those two sections aren't exactly equal, from the pivot point of the top hinge to the pivot of the centre hinge to the pivot of the bottom hinge, the end panels won't fold properly when it's all together!
If the end panel is too loose, you have a couple of choices.
Either take out the side panel screws at the end, get your helper to pull/push the side down a bit more and refit the screws a little higher up the side panel.
Or, take out the end panel, remove the centre hinge and fit some gasket material (strip of rubber seal?) above and below the hinge.
There are other ways to adjust, but they are probably the most straightforward
Then I would fit a couple of screws in the end panel to roof hinges at each end and see how it folds.
Hopefully it will fold flat, so then it's just a matter of lifting it again and screw in the rest of the screws
Anyway, that's my experience from doing three of them - I'm sure others might want to add tips or suggest other ways they might have done theirs.
Cheers,
Robin.