How to wallpaper a room preparation include painting the moldings, doors, windows, ceilings and others. Remove and scrape existing wallpaper. Some papers will take some elbow grease to remove. One may need a steamer ready or handy. Wash painted walls. Put up a wallpaper liner or primer first or at the beginning or start or when or where the existing wall is darker than the incoming wallpaper. The walls shall be sized accordingly. Height of wall shall be measured from baseboard to ceiling in several different areas to get the average maximum height. Add about or 4 inches to the maximum height measurement.
Hold wallpaper up to the wall, align pattern as needed or wanted, add 4 inches and cut. Line up the second strip with the first strip patterns, mark each at bottom and top and cut.
To align the wallpaper parallel or vertical to the wall, mark a plumb line on the wall. Plumb line or device or tool or instrument can be improvised by a piece of string (the minimum length shall be the height of the ceiling) Immerse the string with colored chalk and attach weight to one end. Fasten or hang the string from the top of the wall at the ceiling or from the crown molding while the weight hang down towards the floor. Fasten both end and snap the string against the wall to mark a straight line from floor to ceiling.
Pre-pasted wallpaper will be soaked in a tray of lukewarm water according to manufacturer's literature. Get the paper out of the water onto the worktable and fold the strip with the pasted side inside making a smaller fold at the top and a larger fold at the bottom. Sit the strip for the claimed amount of time in the manufacturer's literature for the water to soak in and the paper to be pliable. Lay the un-pasted wallpaper strip face down on the worktable. Evenly spread adhesive onto the paper with a pasting brush from the center to the edges. Repeat the above instructions for the folding and booking.
Start the hanging of the wallpaper at the remote or conceal place or space in the room behind a door or where the shelf will be located or placed or at the edge or joint at door frame and wall. Align the top section of the wallpaper strip with the plumb line allowing 2 inches overlap at the ceiling. Smooth-en the strip with a brush from the center, to the edges deflecting any air pockets. Unfold the bottom section maintaining or checking the alignment with the plumb line, and repeat the above. Sponge off the un-pasted with clean water as needed or later. Cut the excess paper at top and bottom with blunt work knife.
Repeat the same for the second strip making sure the two strips barely or rarely touch without overlapping. Smooth-en the seams with a seam roller. Continue or repeat the "How To Wallpaper A Room" process for the rest of the strips.