A few more steps...

iOS 13/iPadOS beta profile has started downloading.

Make sure you open BetaProfiles.com in Safari browser.

You will see the following prompt:

Tap Allow from the popup

Then follow the prompts to install configuration beta in Settings app and restart your device.

After your device has restarted, you can receive beta update in Settings - General - Software Update.

Learn how to unenroll your devices to stop receiving developer betas ↗