To do online activation you will first need a Matrix online account, you can register for an account here:
If you have not activated Flowcode before then when you load it up for the first time a box will pop up asking you to enter your username and password, if you cannot see this box, you can get to it by going to the Help >> Activate menu within Flowcode.
In the box shown above to do online activation you simply must type in your Username and Password which you registered with Matrix.
After rebooting, Flowcode now should be activated.
If you have purchased a key and the licence is not correct then you may need to still attach your purchased key to your Matrix account, the FAQ here should give more instructions:
<insert FAQ link>