If you wish to use a spray bottle, fill the bottle halfway with warm water and then add an equal amount of vinegar. Mix the solution well. If you prefer to use a sponge or paint roller, create this same mixture in another container with equal amounts of warm water an vinegar.
Spray or roll an area of wallpaper with the mixture. Don't try and cover the entire room at once because you don't want the solution to completely dry. Let the solution absorb into the wallpaper for approximately 15 minutes.
Scrape off the wallpaper with a large paint spatula.