A Euphorbia acrurensis (Desert Candle) is a lovely plant that can grow to be 5ft-8ft indoors with the proper care. A Desert candle needs as much bright indirect light. High light refers only to bright indirect light since direct sun often burns the leaves of indoor houseplants.
Watering is always tricky. The brighter the light, the higher the temperature, the smaller the pot, the more often the plant will need water. It is always easier to save an under-watered cactus than an over-watered cactus, so when in doubt do not water. Never use water that has passed through a softener, too salty. If your household water has a lot of chlorine or fluorine in it, allow the water to sit out overnight before using it. The plant will probably need water every 3-4 weeks depending upon the conditions in your home. When you water in the spring and summer, water well enough so that it comes out the drip holes in the bottom of the pot. Do not allow the plant to sit in the excess water. Water slowly, so the water can be absorbed well by the cactus soil. The plant will tell you when it needs water. The stems and arms will become soft and the first inch or two of soil will be dry. The plant needs more water in the spring and summer, less in the fall, and practically no water in winter.