USB debugging is a feature of Android devices that allows a connection between an Android device and a computer to transfer data, install applications, read system logs, and more. It is a useful feature for developers and advanced users who want to have more control over their device. Here are the steps to enable USB debugging on a OnePlus device:

1. Unlock your OnePlus phone and go to Settings.
2. Under Settings, scroll down and open About Phone.
3. Find Build Number and tap 7 times on it. You will get a message on your screen that "you are now a developer". That’s it you have successfully enabled developer option on your OnePlus Phone.
4. Go back to Settings > System, scroll down and tap on Developer options.
5. Under developer options, tap on USB debugging. You will see a notification "Allow USB debugging?", click "OK".

It is important to note that manipulating USB debugging can be risky for the security and proper functioning of your Android device. In addition, manufacturers of your Android device can void the warranty if your OS has been modified.