Learn How to Send Bug Reports
If this is your first time trying one of Apple's betas, make sure you understand how to send Apple feedback about the beta's performance.
If you plan on using the developer beta, you'll want to send feedback via Apple's Bug Reporter service. It's fairly straightforward, but you'll want to give it a look and get comfortable with it before you install.
If you plan on using the public iPadOS 13 beta, you'll need to use the Feedback app on the home screen of your device.
For more on the Feedback app and submitting bug reports to Apple, check out Apple's FAQ.