The dome light in your car is supposed to come on when one of the doors is open, as long as the light is put on the proper setting. If the dome light does not come on, the switch may be in the wrong position or there may be a problem with the vehicle. Typical problems with dome lights include burnt-out bulbs and blown fuses.
Inspect the dome light switch in front of the dome light fixture. Most dome lights have three settings: "Off," "On" and "Door." If the "Door" option is selected, the dome light will turn on only when the door is opened. Flip the switch to "Door," and then open the door to test the dome light.
Replace the bulb if the dome light still does not work. Pry off the dome light cover to access the bulb. Use a flat-head screwdriver. Pull the bulb out of its socket and insert the replacement. Ensure that you use the same type of bulb that's currently installed. If you aren't sure what type of bulb it is, bring the old one with you to the automotive parts store. Snap the cover back on and then check the dome light's operation.
Replace the fuse if replacing the bulb does not work. Look in the "Fuse" section of your car owner's manual to determine which fuse powers the dome light. One fuse may specifically power the dome light, or it may power all of the interior lights, such as the map lights and console lights. Remove the fuse panel cover from the location where the specific fuse is stored. Find the fuse number using the diagram on the back of the cover. Pull the fuse out and inspect it. If the fuse is faulty, the metal strip inside of it will be broken. Replace it with the same type of fuse (usually 10A or 5A) and check the dome light's operation.