First, decide how you will be joining the pieces of wood. You can use nails, screws, wooden dowels, threaded studs or joinery. For each you may also use glue to strengthen the joint, but you should not use glue alone.
Second, decide whether you will have a backboard made of a single plank of wood or two dowels. For a plank backboard, you will need to cut a slot in the middle of the upright boards on the frame. You may use a router, or drill and then use a jig or keyhole saw, and or use a chisel. For dowel backboards, you will only need a drill.