The Bluetooth pin number for a device, such as a wireless headset, is normally located in the device's manual or on a sticker on the device itself. When in doubt, contact the device's manufacturer.
Most Bluetooth devices have the pin number or passkey listed in the manual, which might be located online, depending on the manufacturer. Before looking the information up or contacting support, try using "1234" and "0000." Both numbers are commonly used by manufacturers as pin numbers.
Make sure the Bluetooth device is powered on before pairing and that it is properly charged before use. When entering the code, make sure you do it quickly. Many devices only allow 30 seconds for pairing.