Summarize:

You can continue growing your prickly pear in a pot, or you can transplant it into the ground. To transplant the cactus, choose an outdoor location that gets lots of full sun exposure.  Even if you keep the prickly pear in a pot, it still needs to be positioned somewhere that gets full sun. If you live in a climate with colder winters where temperatures dip below 14 degrees F (-10 degrees C), keep the prickly pear in a pot so you can move it indoors when the weather gets cold. The best time to transplant a prickly pear is in the late spring, when the risk of frost and excessive rain are done.  Dig a hole that’s about the same size as the pot the cactus is in. Get the pot as near to the hole as possible. Gently tip the pot upside down and cup the plant with a gloved hand.  Place the roots in the hole and cover it with soil. Pack the soil down with your hands and saturate it with water. During the first week, water the plant every three to four days. After that, water the cactus every three to four weeks. After the first year of establishment, it will not need any extra watering aside from the rain it gets. Let the prickly pear establish itself for several months before harvesting pads or fruit. Wait for the plant to grow a second or third pad before harvesting pads, and wait until there are at least eight blooms on a pad before harvesting the fruit it produces.  Cut pads with a sharp knife in the late morning or early afternoon. This is when the acid content is lowest. Remove the pads just above the joint. Harvest fruit by twisting the fruit and gently pulling it away from the pad. You know the fruit is ripe when the glochids, or thorns, fall off the light or dark colored bumps on the fruit. Be sure to wear gloves to protect your hands from thorns when harvesting from the prickly pear. To prevent damage from the cold, even if you live in a warm climate, cover the soil surrounding the prickly pear with mulch in the fall. If you live in a cold climate and have your cactus in a pot, bring the prickly pear inside in the fall to prevent it from freezing.
Choose a permanent location for the cactus. Transplant the cactus. Harvest pads and fruit once the plant is established. Cover the soil with mulch in winter.