Sorry for the delay!
I've taken some more pics of the Westfalia setup, and the two stickers as well.
I've shown the "swan-neck" removable ball. You have to "prime" the hitch by putting the key in to the side handle, then pulling and turning the handle. This moves the handle round to the red section. It's spring loaded, so once you push the hitch home into the socket (I left the red cover in to make it more obvious!) it springs the lock and the handle goes back to the green section. You then lock with the key and you're good to go. The Westfalia sticker is to remind you to remove the key when the hitch is in use.
Hope this helps!