1. Log in to portal.azure.com and navigate to your web app listed in the App Services tab.
2. Authenticate the APM Insight .NET agent by providing the licensing key. To obtain the license key, log in to your Applications Manager and Navigate to APM tab -> Add Monitor -> .NET Agent > License key -> Copy License key.
3. Copy the license key from the Applications Manager portal and add an app setting key value for the license key & AppManagaer URL in the App Settings tab.

S247_LICENSE_KEY= [Your license key]
APMINSIGHT_HOST=[Applications Manager URL]
For Example:

S247_LICENSE_KEY=APMI_a8569**********************************************6c
APMINSIGHT_HOST=https://apmhost:8443
4. Now, navigate to the Extensions tab in Azure App Services and click Add
5. Select the extension APM Insight .NET Agent based on your application platform.
6. Accept the license agreement for installing the agent
7. Once you've added the extension, restart your Azure App Service to start monitoring the application.