From the update:
So yes, it is happening right now. Just in case you missed your personal email invite: The Pledge Manager is live!
The Pledge Manager is what allows you to tell us which minis you want.
Since we launched it, we've had great feedback, which is pretty cool because we worked hard to make it as comprehensive as possible for you. Of course nothing's perfect, but many backers have told us that they quite like it, and we've been able to quickly improve or fix any encountered issues.
There's a very complete FAQ (in English, French and Spanish) that should answer most of your questions.
Please keep in mind that the Pledge Manager will close on June 17th