You should pay affordable price $1.00 monthly or $10.00 per year.
After making the payment your CWP should be updated to CWPpro within next 24 hours.
You will know that your CWP is updated to CWPpro when you login into CWP and logo on the top left corner is changed to CWPpro.
You can force update check by running this script from the command line
sh /scripts/update_cwp
If your CWP is not changed to CWPpro within 24 hours then you should contact CWP support.
You can always contact our support if you stuck with some issues on your server or you need a security and performance support.
http://centos-webpanel.com/support-services