If you're an administrator for a Dropbox for Business account, you can add more licenses by going to the Account page of the Admin Console.
You'll be able to increase the number of users on your account as well as update your contact information, billing address, and credit card information.
Dropbox for Business equips you with all the space you need. You'll be given 1000 GB when you start your account (5 users). Each additional license you buy will give your team 200 GB of additional space. If you come close to approaching your limit, contact us and we'll work with you to accommodate your storage needs.
This article refers to a feature unique to Dropbox for Business. Dropbox for Business is designed for projects, groups, and other organizations that want to share the same Dropbox storage quota with all of its members. If you're interested in learning more or want to sign up, visit the Dropbox for Business webpage.