Mark the desired location of the wheels on the flight case with a white grease pencil. If you plan on rolling the case when tilted, two wheels installed at one end of the flight case will be necessary. Otherwise, four or more wheels is appropriate for most flight cases.
Measure the depth of the panel you will be drilling into with a tape measure. This measurement will tell you the maximum length of the self-tapping metal screws to use.
Hold the casters against the flight case in the marked locations and mark the location of the screw holes on the flight case with a white grease pencil.
Drill self-tapping metal screws through the screw holes in the casters and into the marked screw holes in the flight case. One of the casters should have a brake to prevent the flight case from rolling away when unattended.