CRM 2016 On Premise (8.1.0.359) Web Api Access using AzureAD

Hey Team, 

I am trying to access Microsoft CRM Dynamics 2016 On Premise using the Web Api, however so far I haven't had any luck. 

What I have done so far:

• Registered an application in AzureAD
• Added permissions to the Application for "Dynamics CRM Online (Microsoft.CRM)"
• Pressed "Grant Permissions"
• Tried to get a bearer token using postman.

This leaves me with 2 problems.

1. I am not sure if I should post to "https://login.microsoftonline.com/common/oauth2/token" or to https://login.microsoftonline.com/{tenantID}/oauth2/token
2. Both times I get the same error: 
   

Any help is most welcome, I am wondering if I should install an extension in order to get this to work? (like this: https://msdn.microsoft.com/en-gb/library/gg309276.aspx).

Regards,

Lars