First, you need get a Pro version.Purchase Gravity Forms Blacklist and Custom Validation
Download from Purchase History page.
Install the download package in WordPress --> Plugins --> Add New.
And you may reference how to install WordPress plugin from here.
Your free version will be deactivated immediately once pro version activated. To avoid trouble it's better to delete free version.
After you activate your license then all functions will be ready for you.Purchase Gravity Forms Blacklist and Custom Validation Pro