You need to add the custom domain name www.contoso.com to an Azure web app named webapp1. What is the first action you must take?

To add a custom domain like www.contoso.com to an Azure web app, the very first step is to create the necessary DNS record (typically a CNAME or A record) with your domain registrar or DNS hosting provider. This record points your custom domain to the Azure web app's default hostname (e.g., webapp1.azurewebsites.net). Without this DNS record, Azure cannot verify ownership of the domain and will not allow you to add it to the web app. Adding a connection string is for database access, not custom domains. Uploading a certificate is done after the domain is added and verified, to enable HTTPS. Stopping the web app is not required to add a custom domain.