If you have bought a Flowcode v6 key from Matrix then it should appear in the form:
The first step is to ensure you have a Matrix account, you can register for a Matrix account here:
Next step is to login to that account:
Finally you want to attach the key you purchased to your account, this can be done by visiting this page here and copying the key into the box provided:
The above screen simply shows you what you currently have on your account, and what you are upgrading into to. If there are any problems here, please contact our technical support to rectify them.
Once you have clicked "Confirm" this will update your licence on our servers and you can then go into Flowcode and go to Help >> Activate and type in your username and password to update your licence.
More information on this process available here: Online activation - Flowcode v6