Go to the plugin page (inside menu "WooCommerce") and use tab "License". You must replace free version with professional version at first.
Renew license
Go to page My Account
Click link "View Licenses", click link "Renew License"
Need more help?
Describe your issue to our support team in the ticket
What do you expect from the plugin?
What the plugin does, what you don't expect
What debugging steps have you already taken (deactivating other plugins, checking js errors, etc.)
