Taking photos in a dark room can be challenging, and using a flash can make for a flat, unwelcoming picture. You want to attract buyers with realistic photos, not scare them away!
Set your camera to take a photo without a flash. You can usually find this setting where you see the lightning rod symbol, on the top or back of your camera body.
Next, you will need a tripod or something to lean on to steady your hand as the shutter on your camera will be open for longer than usual, making a blurry photo if you move. Another trick is to put the camera on a timer so you aren't moving the camera when you push the shutter button.
Turn on as many lights as you can, and try moving or aiming them into darker corners.
Play around with your settings, and even your ISO if you can find it. Higher ISO is good for dark rooms.