The best time to plant them are in the early fall, with transplanting and dividing the bulbs done during that time also. Young bulbs take a few years to become a full bush. Don't be disappointed the first few years after planting your bulbs, it will take a few years for them to become large bushes. After they have developed, you can split the bulbs in the fall and plant in new locations. The more splitting, the more blooms. I bought these bulbs at Walmart 2 years ago for less than $5.00. You don't have to spend a lot of money to have beautiful plants. If they don't come up in one location, transplant them in fall to a new sunny location. They do require full sun to partial sun. After a few years, if you notice low blooms, divide and transplant your plants to a new location. Make sure you support your Peonies prior to blooming.
They are a heavy flower and if you have a lot of rain in the spring, you will find them resting on the ground. I tied tulle around the stems prior to the blooming. String may cut into the stem.
Deadhead the blooms after they begin to fade. Cut the foliage to the ground in the fall to avoid winter damage.