Steps to setup and use Bluetooth on iPhone 8:

• Open the Settings app on your phone.
• Toggle on Bluetooth.
• To turn Bluetooth off, tap the green switch next to it. When the switch is grey, you know Bluetooth is turned off.
• To turn Bluetooth back on, tap the switch once more. When the switch goes green, the Bluetooth is turned on.
• Switch on your Bluetooth device or press and hold the Bluetooth pairing button until the device comes out of pairing mode.
• Press and hold the Bluetooth pairing mode button to return the device to pairing mode.
• Tap the Bluetooth device you want to connect to under My Devices.
• If your Bluetooth device and iPhone are properly linked

Read More: How to disconnect or unpair a Bluetooth accessory from your iPhone 8?