The conference is entirely virtual, online. All the sessions are being given using Google+ Hangouts On Air. To join Google+ visit www.google.com/+.
To register your interest in a conference session, visit the Google+ post that the presenter made about the event. In the comments section below the post indicate your interest. You can find the link to the Google+ Page posts from the Conference Schedule tab. Presenters will make their posts on April 10 & 11th so check back if you do not see it at first.