I want to debug my application by VS but when the application should run, it should have url like: http:localtesting.com instead of localhost. I already have localtesting.com in my host file so directly putting that url in my browser opens my IIS default directory page. How can I make my VS to run on that url while debugging? Where should I put that url?

Edit:
Putting the url in custom web server textbox and running the solution I am getting :

As @SteveHobbs said, set it to “Use Custom Web Server and put your URL into that box. Just underneath that section, there should be another section labelled “Debuggers”.
Put a tick into the checkbox next to ASP.NET and save the properties.
When you want to debug, go to the debug menu within VS and choose “Attach to Process…”.
If you are using IIS, look for the process called ‘w3wp.exe’ and choose that. After a bit of crunching, perform whatever actions you need on your web app and you will see the debugger land on your breakpoints and so on.