If you are an IT person looking to allow employees to integrate their own calendars (work or personal), here are the steps to do so:
1. Navigate to portal.azure.com
2. Click on Enterprise Applications in Azure services.
3. Click Consent and Permissions on the sidebar under Security.
4. Allow user consent for apps either on the user level or the group level if you are managing users via groups.
5. Keep in mind that these are blanket permissions for all apps, not just for the Together app.
For information on how a user can integrate their individual calendars, see this article.