You don't register for sessions, you just add them to your schedule.  All are first come.  There are only a few that usually require early attendance to get a seat.  Some are very hard to get seats for.  Some are just pretty crowded.  Some are fairly empty.  Adding them to your schedule helps with room planning.  The schedule usually shows up much later.  I think a little over a month prior last year.  Hopefully someone working with the conference has some details.  Even just some session info would be great.  Or potential speakers.