If the drawer is a bit too narrow for the opening, shim the slides out from the cabinet using a piece of paper or cardboard. The runners of hidden slides cannot be removed. Drawers are held on top of the runners by hooked tabs at the back corners and a pair of clips under the front, behind the face. Installing the slides on the sides of a cabinet is fairly straightforward, much like other side-mount hardware. Proceed from top to bottom, cutting the plywood as you go.
Commercial jigs are also available for predrilling mounting holes.
The drawer part of the project is where things get different. For a typical hidden-slide design, two clips are screwed to the underside of each drawer. Screw the clips to the front of the drawer, which is usually made of thicker stock than the bottom. Although the mounting holes in the clips may be used to guide a drill bit when predrilling, jigs and special drill bits are available, and they do help. Use a piece of scrap plywood to position the slides inside the case.