To get a Christmas cactus to bloom indoors, you need to provide the right environmental conditions. Make sure the plant gets plenty of bright, indirect sunlight during the day. You should also keep the soil moist, but not too wet, and provide enough humidity for the plant to thrive. Finally, give it a boost by adding a balanced fertilizer to the soil once a month during the growing season. With the right care, your Christmas cactus will be blooming in no time!