All you have to do is dig up the roots and plant them about 3 or 4 inches under the ground. Really, you can almost just throw them on the ground, and they'll come up. They'll just grow wild, especially on the edge of a field, and it won't cost you a thing. Full sunlight is preferable, but blackberries will thrive in partial shade. Frost is rarely a problem, but it's a good idea to avoid frost pockets.
Blackberries grow in a wide range of soils, but they fare best in well-drained soil.
Ideally, pH should be 5.5 to 6.8. For row planting, allow at least 8 feet between rows to provide room for humans and animals to walk between rows. Erect blackberry plants can be planted as close as 3 feet apart, but some of the longer, trailing varieties should be set 6 to 8 feet apart. The optimum planting season is in early spring. To plant, dig a hole wide enough and deep enough to take the roots.