Plant 2–3' apart with the eyes (where the growth shoots meet the root) no more than 1–1½" below the surface in well-drained soil, full sun to partial shade. Peonies are extremely long-lived so amend the soil richly when you plant. Compost, very well-rotted manure, bone meal and azomite are all recommended. After that they need only a bit of weeding and feeding to flourish.
Mature plants often need staking or tying because flowers and buds can be quite heavy. For big plants, I’ve been using a chicken-wire method that Mary Fowler recommended. Cut a flat circle of chicken wire 2 or 3' in diameter and place it on the shoots when they are 8–10" tall. The shoots lift the wire, grow through it and use it for an invisible support.
Remove spent flowers after blooming, then cut dead foliage to near ground level in fall. Plant along the driveway; a heavy snowbank doesn’t bother them.
Herbaceous Perennial Plants
When you receive your order, open the bags and check the stock immediately. Roots and crowns should be firm and pliable. Surface mold is harmless and will not affect the plant’s future performance. Store plants in their packaging in a cool (35–40°) location until you are ready to plant. If it’s going to be awhile, you can pot up your perennials.
Do not plant bare-root perennial plant crowns directly outdoors before danger of frost has passed. Wet and/or cold conditions for an extended period may cause rotting.
For more info:
About planting bare-root perennials