If you're in a cold climate, the only way to grow Dragon Fruit cactus is indoors. Provide it with a lot of light, and choose a plant that suits your space. Indoor ornamental Dragons are best started as seeds. Once mature, this plant takes up a lot of space, so starting with a seed will buy you a lot of time.  If you want a fruit bearing plant, it's you'll need to set aside a significant amount of space. Even just one plant will take up an easy six feet square. They're terrifically spiky to so give them lots of clearance. They need a lot of light to grow that delicious fruit too. Indoors that's best achieved with a LED grow light.