So if you have an existing DigitalOcean account, it makes it seem like you can't apply the promo code to it. But I shot off a ticket to DigitalOcean's support, and they applied the $100 promo to my account within 5 minutes. So definitely send them a message if you have an existing account that you would like to have the credit applied to.
Awesome pack, and great service from DigitalOcean as well.
Also of interest is that my account is apparently already flagged as a "student account" since I've gotten the 5 free private repos in the past with it. Which means once I hit "Get your pack" it immediately gave me access.