The plants should be dormant when transplanted. In mild climates, you can move them in either in early spring or fall, after they've dropped their leaves. In cold regions, move them in the spring, before bud break, so they'll have the summer to get established before having to face the harsh winter weather. First, do your annual maintenance pruning. Next, make sure the new planting site is sunny with well-drained, moisture-retentive, acidic soil (pH 4.5-5). If the soil isn't this acidic, mix sphagnum peat moss into the backfill from the planting holes. Water them well after transplanting and through this coming year while their roots rejuvenate.