Need download beta iOS 14

iOS 14 beta is not available. An iPhone 6 Plus cannot be updated past iOS 12. You need a newer phone.

1. Back up your device using iCloud or your computer.
2. Plug your device into power and connect to the internet with Wi-Fi.
3. Go to Settings > General, then tap Software Update.
4. If you see more than one software update option available, choose the one that you want to install.
5. Tap Install Now