Your organization may be a customer of Microsoft online / cloud services such as Office 365. If so, you should try logging in with the same work or school account you use to login to Office 365, etc. Give it a try! It it doesn't work, create a Microsoft account.
(UNC folks, please use firstname.lastname@example.org as your username.)
The Carolina Population Center is a community of scholars and professionals collaborating on interdisciplinary research, methods, and training that advance understanding of population issues.