If you are trying to login for the first time using your invite code and having trouble finding a text field to place your invite code in, you should press the Log in button on the right top corner of the screen. After pressing it, you should see the following login window:
In order to log in for the first time to Dreamler, click on the Sign up link in the log in window. This window has a dedicated text field for your invite code.
If you experience issues with your invite code contact Olof (firstname.lastname@example.org).