Step 2: 9V battery, battery snaps and little pocket
To connect the 9V battery snaps to the conductive traces, strip the ends of the wires that come out of the battery snaps and make a little loop. Solder this so that it does not unravel. Use conductive thread to sew the loop onto the end of the fused conductive trace.
You will want to make a pocket for your battery. Best to use stretchy fabric and cut it a bit smaller than the actual size of the battery so that the stretch will keep it in place. Also, make the pocket 2 or 3 cm longer than the battery, this way it stays in nicely, even when upside-down.