If you're planting them out into your borders, they need a sunny position with some compost dug in around the roots as they grow very quickly. You should be able to plant them out into the open now the risk of frost is over. Keep them watered in dry weather. Some of the very tall varieties may need staking with a stick if they're in a windy position. And when they've finished flowering and the seed heads appear, let them dry as the birds will enjoy eating the seeds which contain a lot of nourishment.