
Explanation

Box 1: App Service plan
To bind a custom SSL certificate (a third-party certificate or App Service certificate) to your web app, your
App Service plan must be in the Basic, Standard, Premium, or Isolated tier.
Box 2: A Record
You remap A record for IP SSL.
References:
https://docs.microsoft.com/en-us/azure/app-service/app-service-web-tutorial-custom-ssl