First, you need buy pro version first.
Go to your WordPress Dashboard --> Plugins --> Add New and then click "Upload plugin" button on the screen.
Chose the package ( zip ) file and click "Install now" on the screen. Also remember to click "Activate plugin" after the package uploaded succesfully.
If you have free version installed & activated then once pro version activated it will deactivate your free version.
With the admin notice you may delete the free version.
Enter your license and activate it.
Purchase Contact Form 7 Blacklist