When administering Office 365, the left navigation pane contains a link to the Azure Portal. This is quite convenient for bouncing around the various sites. However, not every Office 365 administrator is also administering Azure.
For developers, this becomes more problematic. If you get a demonstration tenant, or a trial tenant or a developer tenant, the link to the Azure Portal prompts you to sign-up for Azure. But all that is typically needed is to manage users, groups and applications.
What is more appropriate, in my opinion, is access the new Azure Active Directory Portal instead. (Add your vote to User Voice!) The AAD Portal allows managing the directory that powers the Office 365 tenant, including applications. This is a much better option for developers.
As an alternative, I add a custom tile to the app launcher. As a public service, I'm hosting an appropriate-sized icon at https://schaeflein.ghost.io/content/images/2017/06/AADPortalTile.png.
Enjoy!