Task: The following guide will provide you with instructions on how to create app registrations.

Prerequisites: Make sure you have appropriate license to access portal.azure.com

Instructions:

Step 1: Login to portal.azure.com and Click on Azure Active Directory.

Step 2: Now Click on App registrations

Step 3: In the App registrations page, Click on New Registration.

Step 4: Type in the name of the App registration, we can type in as "Microsoft Graph API". Under Supported account types Click on "Accounts in this organizational directory only" and leave the Redirect URI blank.

Step 5: Now on the Microsoft Graph page, Click on "Certificates and Secrets"

Step 6: Click on "new client secret"

Step 7: In Add a client secret, insert description as "Subscription Status" and for Expires Click on "24 months." Make sure to copy the value of the secret and store it in a safe place as once you move away from the page that secret will be masked (will not be visible).

Step 8: Now Click on API permissions and then Click on Add permission.

Step 9: Click on Microsoft Graph.

Step 10: Click on delegated permissions.

Step 11: Search for "organisation" and add both the permissions from there. Search for "directory" and add the 3 permissions from there and save the changes. Then Click back on Add permissions, select application permissions and do the same (directory and organisation permissions).

    
Step 12: Click on grant admin consent and then Click on Yes.

Step 13: Go back to Azure Active Directory and take note of the Primary domain.

Step 14: Populate the information directly into Microsoft Graph API integration section on the account form in Dynamics 365. The Tenant ID, Client ID and Secret is from the App registration. The Tenant domain is from the overview screen in Azure Active Directory. The Audience is https://graph.microsoft.com 

Outcome:
Your app registration as been successfully created.

Further Reading:
https://docs.microsoft.com/en-us/azure/active-directory/develop/howto-create-service-principal-portal