Sign up to be one of the first to test it
has opened up the registration for Project Spark that was shown during the Microsoft press conference at E3. Once registered, you get a confirmation Email saying that you are registered, but it will be some time before you will hear if you are in and able to be a part of the beta and of course you will have to wait tillt he console is released.
The beta for Project Spark is set to begin right out of the gate once the Xbox One is released (during what we believe is the last week of November). According to a number of sources, Project Spark will be free for users to download. Additional add-ons and stuff will be sold to fund the game long-term, but it is basically free to download and use.