Cutting tool with multiple blades. You can buy each of the tools you need separately or in a wallpaper hanging kit. They will be available everywhere wallpaper is sold, and at hardware and building supply stores. You will need a good brush to smooth wallpaper down and push air bubbles out from under the paper. You might substitute a squeegee , basically just a thin piece of plastic, used by placing the edge against the paper and pushing the air bubbles out from the center.
Some papers call for using a sponge for smoothing.
If your paper shows brush marks or you have a vinyl, which can stretch, consider using a sponge. A straightedge, usually made of metal, helps you cut a straight line in critical areas, like at the ceiling line. It is very important to have a nice sharp blade every time you make a cut. Several kinds of cutting tools are available. A small razor-blade caddy can be very handy.