Assuming you have a boat with an inboard engine and outdrive, the following should work to bypass the neutral safety switch. Keep in mind that this is not recommended as a permanent solution, and you should only do it if absolutely necessary:
1. Locate the neutral safety switch. It is usually located on the engine or near the shifter.
2. Disconnect the wiring harness from the switch.
3. Use a wire jumper to bypass the switch by connecting the two wires that were previously connected to it. Make sure that the jumper is secure and won't come loose while you're operating the boat.
4. Test everything before taking your boat out on the water!