Accessing Dialogue Studio
You can access Dialogue Studio via the Infinity Admin Portal, see the link provided:
Note
Please select your matching regional admin portal.
AnywhereNow admin Portal (Production NORA)
AnywhereNow admin Portal (Production EMEA)
AnywhereNow admin Portal (Preview)
To authenticate, simply use your Microsoft account that is licensed for Infinity. This will allow you to access all the features of the Infinity Admin Portal.
Note:
The account that is trying to authenticate should have been assigned Dialogue Studio Editor user privileges. This can be assigned via the Admin Portal, see Users privileges
Once you are logged in, you can access Dialogue Studio via the left menu (1), and select Go to Dialogue Studio (2):

If this is the first time opening you will first see this notification (1):
Wait about 3-5 minutes for Dialogue Studio to setup, after this you will see a new notification (1):
You can now start using Dialogue Studio.