By default a SharePoint App-project use IIS Express as web server. And if you deploy your App from within Visual Studio using Ctrl+F5 you will get URLs similar to https://localhost:44305
If you want to use a predefined IIS site with http://Apps-12345678ABCDEF.ContosoApps.com bound as host name then you can try this:
- Open your web project in Visual Studio
- Open Project Properties (right-click on the project)
- Click on the Web section
- Under the Servers heading change from IIS Express to Local IIS and also update the Project Url.
As an alternative you can Publish your app from the App-project.
- Right click project and select Publish...
- Click Package the app
- Enter your DNS/URL in the field Where is your website hosted?
- Deploy the App to App catalog or directly to the web site