Activate Pro version of Macs Fan Control

Once you purchased a license and received the license key, click on the Macs Fan Control icon in the Menu Bar, go down to the 'More' submenu and click 'Upgrade to Pro version' as seen below:

Then press the 'Enter License' button:

Enter your email and the code and press the 'Unlock' button. When a license is for multiple computers, the code must be entered on each one.