The positive speaker wire that we just separated is used to connect the negative terminal of the receiver battery pack to the negative terminal of the recording module battery. Take one end of the positive wire and insert it into the negative terminal of the 9 volt battery. Then attach the 9 volt battery connector for the recording module. This should pinch the wire and hold it in place. Then take the other end of the wire and wrap it tightly around the negative terminal of the receiver battery pack. Once you have everything mounted, the wires should stay in place. But if you want everything to be extra secure, you can tape them in place. I do not recommend trying to solder wires to a battery terminal.
The negative speaker wire will be used to connect the receiver output transistor to the play pin on the recording module. One end of the wire is already connected to the output transistor. So we just need to connect the free end to one of the play pin holes that were mentioned in Step 2. You don't need to solder the wire to the recording module. You can make a good connection by just twisting the wires together around the board. To do this, Insert a few strands of the wire through one of the holes (the hole is probably too small to fit the whole wire). Then twist the strands of wire back together. As long as wires are tight, it should make a good connection and stay in place.