In the tutorials (on YouTube) they show edublogs

In the tutorials (on YouTube) they show edublogs as the example site for Pro Sites. During their signup process there is a place where it says enter username/blogname (blog.edublogs.com). I would like for my form to be similar to this. I used the “Profile Builder” plugin which was recommend by a WPMU staff member to offer more than the normal wp-signup.php page.

How do I offer them to create their username/blogname? Additionally, I signed up as a user through my signup form, but it does not create the subdomain (which is the way I set up my network). I have Network Settings > Both sites and user accounts can be registered - and I assumed this would allow for subdomain creation upon signup.

Any help would be appreciated. Thank you.