Verifying your license key for User Registration addons allows you to have access to automatic updates right on your dashboard. Here is how you can verify your license key.
Go to your account page and click on the License key tab.

Copy the license key.
You will need the User Registration Pro plugin installed and activated. Now, go to User Registration > Settings > License. Insert the copied license in the License Key input field as shown in the figure below.

Now, hit Save Changes and you have successfully activated the license for premium add-ons.
You can confirm this by visiting your account page ->License Keys ->Manage Sites. Your activated site URL will be listed there.