Alright, going to clarify. Jessikia actually gave the right answer I was just being dense.

In your email, near the bottom, it will have a link that will guide you to a special page for you to put in the pre-order bonus code. That will then give you a larger, appropriate code for you to enter into the pre-order registration page.

I kept looking over the fact the email had such a link thinking it just took you to the pre-order registration page.