Step #1: After the plugin activation you will see this page.
If you bought the plugin directly then you should recieve a license key in your email. Enter the license key and click on “Agree & Activate License”

Else: Click on “Activate Free Version”.

Step #2: Click on “Allow & Continue”.

Step #3: Click on “Upgrade”.

You will see this page to upgrade

After successful payment, The plugin will be automatically converted to pro version