I've never heard of a 'wet' method of applying vinyl decals. Doesn't mean it doesn't exist, but you'd think I'd have run into it by now. The application sheet they refer to is what I call a carrier sheet. You peel it and the decal off the backing, apply and burnish it then peel off the carrier, leaving the decal behind on the surface. It's a way of ensuring that multiple-piece decals stay in alighnment.

There's a couple ways of keeping decals in alignment during application. If it's a panel-type decal, you can wrap some masking tape around the tube, making a 'fence' to but one end of the panel against. You can also use one of these fences to but a ruler against and make light pencil lines on the frame tube.

Can you scan your decal sheet in for us so we can see what you're dealing with?