Prepare your pot. Put your hanging container or pot into the hanging basket. The pot should fit the basket snugly so that it stays in place, doesn't move too much.
Fill the pot with soil for the blackberry plants. Most soils are appropriate because most blackberry plants are hardy. If you are unsure about the best soil for your particular climate, ask at the store where you buy the blackberry canes which fertilizer and soil is best for your situation.
Transplant your blackberry canes to the hanging pot. Gently dig it out of the pot it comes in, adjust the soil in the hanging pot, and put it into the new pot. Break up the soil around the roots to allow better growth, and then cover the roots with the soil.
Put in support sticks to help keep the blackberry bramble small and give the plant something to climb on. Hanging the plant means that it has limited space to grow, so you want to provide a little extra support to keep it small and allow some climbing growth.
Hang the blackberries up on a hook and water each day, or as appropriate for the specific variety.