With any prepasted wallpaper, you'll need to activate the paste prior to hanging the paper. There are different activation methods, however, and you'll need to read the instructions for the paper you're using for the exact method and you'll need to follow those instructions to the letter or your wallpaper might not adhere properly.
The most common activation method is to roll up your cut strips from the bottom with the paste side out and the pattern side in and to submerge the rolls one at a time in a tray full of water for the length of time indicated in the instructions.
With most papers, you then pull the strip up out of the water gripping the top and unrolling it as you pull and lay the strip out for booking, which is described below.
Some papers, though, must be applied directly to the wall after activation in water so you skip the booking step and go directly to the hanging step described below.
Some prepasted wallcoverings can now be activated with a water-based mixture applied to the back of the paper with a roller. This eliminates the need for soaking the paper in water and makes it a bit easier to handle. As with any paper, follow the instructions as to the specific activators and installation techniques.
NOTE: Whether you're using prepasted or unpasted products, don't do all your strips at once--especially on your first wallcovering job. Putting up the first strip may take a while, so it's a good idea to start with just 1 or 2 strips, book them, hang them, see how long it takes you and then determine how many you should be pasting at a time.
Preparing Unpasted Wallpaper
The simplest way to apply wallpaper paste to unpasted papers is to pour the paste into a clean paint roller tray and use a paint roller with a 3/8-inch or 1/2-inch nap to spread it over the paper.
It works best if you can rent a long wallpapering table so the paper doesn't drag on the floor. But you can manage with any clean, flat surface. One option would be to spread a piece of plastic on the floor, lay the paper face down on that and roll the adhesive out on the back.
As always, follow the manufacturer's instructions, using the recommended adhesive and applying it as they recommend. Once the strip is covered with adhesive (don't leave any dry gaps), book each strip as described in the step below.
Most wallpapers will require "booking" after activating the paste on prepasted strips or spreading adhesive on unpasted ones.
That means gently folding the ends of each strip back to the middle so that the pasted sides are touching, lining up the edges as carefully as possible. Don't crease the folds, though, or you'll leave a permanent mark.
Then you fold it in half again, lining up the ends. And you finish the booking process by loosely rolling the strip up from one end to the other.
This is a critical step for most wallpaper, because it lets the paste penetrate the wallpaper, keeps the paste from drying out before you hang it and allows the strip to "relax". Follow the instructions closely as to how long you should let paper book before hanging it.
Remember that some papers don't require any booking at all so, at the risk of being repetitive, check the instructions carefully for the details on the wallcovering you choose.