Visit ​myap.collegeboard.org

Log in to your College Board account.  If you have ever taken an AP exam or the SAT, you have an account.
Once logged in, click "Join a Course or Exam" and use the appropriate join code below:

5th period code:  XYNARQ

6th period code:  DA67Y3

To access assignments, click the AP Classroom button (marked by "2" in the pic below).  If anyone finds a direct link, please let me know!