What you first need to do is either ask for an account directly through Pinterest or get an invite by an already registered member of Pinterest to send you an invitation to join.
At this time, these are the only two methods for you to gain access to the site. The waiting list and length of time for you to get accepted varies, so your patience may be needed. However, if you happen to get an exclusive invite from a member friend of yours, then you may be able to …