They can be bought from garden centres already growing with the bud just about to burst in time for Christmas Day. Alternatively, you can buy the bulb gift wrapped with instructions on how to grow. In this case they usually take around 6-8 weeks after planting to flower.
Originating from Brazil, they need a frost-free environment such as a warm, bright windowsill. Then, they can be moved outside once the frosts are gone and the nights no longer cold until summers end.
Give them well drained soil and plant the bulb with one third above the soil and, with a bit of care, the flowers should reappear year after year.