dig over the soil where you want to plant, a larger area than you'll need just to plant it in, incorporating humus rich material such as soil conditioning compost from the garden centre, or well rotted horse manure, spent mushroom compost, leaf mould, that kind of thing. Then turn the plant out of its pot, dig a hole wide enough and deep enough to accommodate the size of rootball you have, unwind or tease out the coiled up roots, if you see them, and plant. Water well with a couple of gallons of water or leave the hose running onto the area for half an hour or so. Keep watered subsequently.