Some teachers want a head start on the PTs or might want to make sure they have everything set up well ahead of time. I got an email from College Board on Wednesday 9/20 titled "Important AP Resources for You" (and I assume you did too if you completed the audit). The email contains your individual access code needed to start your class' Digital Portfolio.
Once you login, you should be able to create your sections of CSP and then students will be able to login and submit their PTs (although now is a bit early). Teacher and student instructions are linked in that same email.
Last year later in the year a few teachers asked where they could find their access code, so... this is said email that contains your individual access code needed to setup your class' Digital Portfolio.