In order to add a new account, enter your email address, set a password and click on Create your account.
You will automatically log in and get the access to the demo studio.
But you still don't have the opportunity to create your studio or game on this step. In a few minutes, you will get an email. Click on FINISH REGISTRATION button and get started.
If the button doesn't work, you can get its link (by using context menu) and paste it in your browser.