Dampen the curled wallpaper with a sponge dipped in warm water, but don't soak the walls. Wait a few minutes and dampen the wallpaper again. Repeat several times, until the edges lay flat.
Dry the area as much as you can, using a towel or dry sponge. Spread premixed wallpaper paste to the back of the wallpaper edge, using the artist's paintbrush. Brush some of the adhesive onto the exposed wall surface. If you have to mix the paste, follow the label directions and let it sit for a couple of minutes before applying it.
Wait a few minutes for the paste to absorb, then smooth the wallpaper down. Press it firmly in place by running your seam roller over it. Don't press too hard, or all the paste will squeeze out.
Let the paste sit for about 10 minutes. Wipe a damp sponge across the area to clean any residual paste off the wall.