Soak the soil in the planting hole. Then take a rhizome
division and place it in the center of the mound. Spread the roots around and down the mound. Cover the division with soil, being careful not to bury the rhizome with more than an inch or 2 of soil. Remember, it will probably settle a bit lower and bearded iris will rot and certainly won't bloom, if buried too deeply.
Water well and do so weekly until you start to notice new growth. Then enjoy for another couple of years.