Hit the "Forgot your password?" link. Put in your email address. If they have you in their system they will send you an email. The account number will be in the email.
Thank you, sir. This helped me log on and figure out what the problem was. I hadn't received any issues yet, despite having signed up over two months ago.
It turns out, they had a really old address on file for me, even though I gave them my new address when I signed up in July. Thanks to your suggestion, I was able to log on and update my address. It shows the Oct issue already shipped, unfortunately, so I think I am SOL for that one too.