How to set up a new WordPress website on Azure App Service

Great blog !

Im actually going to use it for one of my customers.

I got a small question, how can i make this wordpress site fully https with a custom domain behind an Application Gateway ?

I am already able to make it available through Application gateway, but if i want to open a post page then its still pointing to *.azurewebsites.net.

I have searched on the net, should be able to change the site url , but it is grayed out .

have tried to follow this >> How-to For WordPress on App Service (WindowsLinux ) - Azure App Service 

any tips on that ?