Check the width of your paper (rolls vary in width starting at 20-1⁄2 inches), and plan to make your panels the same width (they can be as tall as you want). Hang kraft paper mock-ups on your wall to determine where you'll place your final panels. Our panels are 68 inches tall and 29 inches wide (27-inch-wide wallpaper plus two 1-inch-wide moldings).
A wallpaper tool kit contains everything you'll need to apply wallpaper, including a paste brush, smoothing brush, seam roller, and straightedge. Look for a wallpaper paste designed for use on painted surfaces. This one goes on pink but dries clear. You'll need a sponge to clean the wall surface before applying paste and to clean any excess paste off the wallpapered surface before it dries. Following the manufacturer's directions, apply wallpaper strips to the wall at your determined locations. Use a level to be sure your placement is straight.
Cut the ends of your painted molding pieces at 45-degree angles with a clamping 12-inch miter box and saw. Sand the edges where you made cuts so the pieces will join together tightly, and create a frame around your wallpaper. Load a tube of construction adhesive in a caulking gun, and apply adhesive to the back of your molding strips. Place the molding to frame the wallpaper panel, lining up the inner edge of the molding with the outer edge of the wallpaper; press in place.
When adhesive is dry, use a finish nailer and pin nails -- not a hammer -- to secure. Use nail-hole filler to fill any visible holes. We like one from Goop because of its built-in applicator, and the white matched our trim paint color exactly.