The button consists of four parts. Two of them are installed on the wrong side of the fabric, two on the front.
Select the location where you want to install the button and pierce a hole with a hole punch or a hot awl. The diameter of the hole will depend on the density of the material, but it must be slightly smaller than the diameter of a leg of a button. Typically, it is 2-4 mm. through the opening leg of the outer part of the button ("hat").
Put on leg on top of the cloth castle is the part of the button, which is spring. Put on both sides of parts a piece of cloth or rubber. This is necessary in order to avoid scratches and damage fittings.
Fasten button detail with a hammer or pinch them with pliers. Do the same with the second half details.