Brassicas are a family of cool weather crops that includes broccoli, cauliflower, kale, bok choi, cabbage, and brussel sprouts. These kitchen staples can all be planted early in the spring. I have had the best luck starting them indoors in February and planting them outdoors in mid to late March. You can also buy the starts from a nursery.
Dig a hole the size of the pot the plant is in. Gently tilt the plant out into your hand with the stem between your fingers. Pinch the bottom of the pot to loosen the roots and it should slide out smoothly. Place the plant in the hole so that the top of the soil is level with the base of the plant. Fill in around the roots with loose soil and gently pack it in. Be sure to mulch and water right away. Water about every 3 days or when the soil is dry one inch deep. See the link below for information on harvesting.
Links to More Information
Year of the Brassica, all about Brassicas https://ngb.org/year-of-the-brassica/
Tips for Harvesting Brassicas https://sierraharvest.org/tips-for-harvesting-brassicas/