Hi Amsterdam plant it at the same depth it was growing at in your friends garden. there should be a 'tuber' that needs to be just under the surface on this type. they don't mind a bit of shade either. if it doesn't have a bud present now in the leaf cluster it wont flower this year. pests on mine tend to be ants feeding on the sticky bud secretion. water well if it is very dry otherwise that's ok.

choose its site with care as they don't like being moved about as the fine roots that collect the water are easily damaged. If it hasn't been in the pot for long get it in the ground quickly. if it has been potted up more than a week or 2 then leave it in the pot for about a month to give it chance to develop some good roots then plant it out with as little root damage as possible.

seaburngirl- Thanks for your advice. I think the peony has come from a nursery so best plant it out asap?