Back two years ago they sent a physical letter, and the candidate number was printed in the top right.
Check the email again, the candidate might be there. Or wait for the letter.
When the application opens, you'll be able to access CIS with the candidate number and your social security number. For me, the application was available by the time NASS Session I was over (I remember starting on it as soon as I got back from NASS). And I was able to do so several months earlier than the folks who didn't apply to NASS and didn't get candidate letters until July.
Edit: Just read your post again. You have to be accepted to NASS first. The NASS acceptance letter has a candidate number.
Either way, the point is: Apply to NASS. Apply to the Academy. If you don't get it, at least you tried.
"The credit belongs to the man who is actually in the arena, whose face is marred by dust and sweat and blood; who strives valiantly; who errs; who comes short again and again; because there is no effort without error and shortcoming, [...] who at the best knows the triumph of high achievement, and who at the worst, if he fails, at least fails while daring greatly, so that his place shall never be with those cold and timid souls who neither know victory nor defeat."