My opinion: the negative (ground) side of the battery is connected directly to the negative wire of the reel motor (hopefully it is marked). The positive (hot) side of the battery is connected to the fat terminal of the relay. (Should be marked "B"). One of the switch wires is also connected the aforementioned fat (hot) terminal. The other switch wire is connected to the thin screw of the relay. Finally, the remaining fat wire from the motor is connected to the fat terminal of the relay, (should be marked "S"). (Meaning switched).