When you click on the button "Create" on the register overlay an email with the activation token is sent to the email address inserted and the "Activate Account" overlay screen will appear.
If for some reason the register overlay has been closed after you have clicked on the "Create" button, click on the link "Register" on the top right.
The register overlay will open and you can click on the link "Activate Account" on the overlay left bottom.
The "Activate Account" overlay screen will open for you to input your email address and the token you received by email. Fill-in the information and click on the button "Activate Account".