Flip the drawer over so the bottom faces up. Measure and mark where the glides will go near the bottom edge on the right and left sides of the drawer with a measuring square and a pencil. Check your measurements with a level.
Drill holes with a portable drill where you marked the drawer if there are no pre-drilled holes already. Install the glides on both sides of the drawer with screws and a screwdriver. Ensure that the glides are installed straight by checking them with a level.
Measure how much clearance the front of the drawer will need in the cabinet with a measuring tape and cut a wood spacer the width of the needed clearance with a band saw. Clamp the spacer to the inside front of the cabinet with woodworking clamps.
Insert the drawer part way into the cabinet and mark where the glides will go on the left and right interiors of the cabinet. Check the measurements with a level to ensure that the glides will be installed straight on the interior cabinet walls.
Drill holes with the portable drill where you marked the interior walls of the cabinet. Install the glides on both sides of the cabinet with screws and a screwdriver. Check the glides with a level to ensure they are straight. Insert the drawer to determine that the glides are lined up correctly.