Navigate to this Microsoft article.
Follow all the steps. For Step 3, enter a relevant application name (e.g., “Marketo Integration”). Under the Supported Account Types, select Account in this Organizational Directory Only.
Write down the Application ID (ClientId) and Tenant ID. You’ll need to enter it in Marketo later.
Grant Admin consent by following the steps in this article.
Generate a Client Secret in the Admin Center by clicking Certificates & secrets.
Click the New client secret button.
Enter a client secret description and click Add.
Make sure to make note of the Client Secret value (seen in the screenshot below), as you’ll need it later. It is only shown once, and you won’t be able to retrieve it again.
Follow steps from the following link to set up an application user in Microsoft.
Federated Azure AD to ADFS Onprem needs the creation of a Home Realm Discovery policy for the specific application. With this policy, Azure AD will redirect the authentication request to the federation service. Password hash synchronization has to be enabled in AD Connect for this. For more information, please see OAuth with ROPC and Set an hrd policy for an application.
Additional references can be found here.
Almost there! All we have left is to inform Marketo Solution about the new user created.
Go back to the Advanced Settings section and click the icon next to Settings, and select Marketo Config.
If you don’t see Marketo Config in the Settings menu, refresh the page. If that doesn’t work, try to publish the Marketo Solution again or log out and back in.
Click the search button on the Marketo User field and select the sync user you created.
Click the icon in the bottom-right corner to save the changes.
Click the X in the upper-right to close the screen.
Click the icon next to Settings, and select Solutions.
Click the Publish All Customizations button.
If you’re upgrading from Basic Authentication to OAuth, you can use this article to reconfigure your authentication.