You can start by turning the rheostat on the instrument cluster, the black knob sticking out of the speddometer face. This controls the brightness of the instrument lights. If you feel "roughness" when turning the knob, turn it back and forth vigorously to clean the contacts. If you get no response when turning this knob and your lights do not come back on, then it is time to replace the rhestat in the instrument cluster. Cost about $35-40.
Good luck