I have Paeonia officinalis Rubra-Plena, the deep red one, grows around three-four feet high needs to be staked well as if flowers May-June and usually when we have high winds that can knock the large flowers down.
My other ones are Paeonia lutea Chromatella yellow again around three feet or a bit more and also needs staking, I only get half the flowers that I get on the Rubra and much as I love them often wonder if they are worth the space they take up.
Plant them in a spot sheltered fro early sun after a frost but then they need sun the rest of the day so south and west facing is good.
Plant them with the crown just clear of the soil or they may not flower, rake in some bone meal and water in well then once a year mulch with well rotted manure if you can get it or good compost, keep the mulch back off the crown, never cover that and spread it well around the plant.
After flowering I dead head them leave the plant alone until spring, books will say cut back the foliage in Autumn when it dies off I found it a good frost guard for the crown so cut it back as spring arrives, a little late this year. I grew up with a bushy shrub of Rubra that was fifty years old when I was a bairn and still going strong 30n years later, I have a cutting of that plant. A position sheltered from the winds is better for them.