Coincidence. I've just put down the new Land Rover World mag and there is a letter in there from someone who has exactly your problem - ie no instructions on how to fit his WVA carrier! He had two and found the second much easier to fit than the first, which is probably not reassuring for you! He also resorted to going to a Scorpion-Racing stand at a show and photographing the carrier fitted to their demo vehicle. Good luck, and if you find out how to do it let us know because I'm in the market for a wheel carrier.
(The writer to LRW was mainly saying about how a huge bend had developed in the handle of his hi-lift jack which was mounted on the WVA carrier. He concluded that water had collected in the handle whilst it was on the back of the l/r and had then frozen, the forces involved bending the steel.)
(Also, how much £ is the WVA carrier? Scorpion annoyingly don't put any prices on their web-site or mag ads.)
Cheers,
M