Unfortunately, there's no way that I know of to add authentication to a VS2013 project after you've created it, but you can add it on project creation.
Create an ASP.NET project and then click "Change Authentication" when it prompts you to select a template.
You then want to choose "Organizational Accounts" and choose "On-Premises" from the drop-down menu. I know ACS isn't what you were normally think of as "on-premises" but that's what you want. Then enter your metadata document URL. You can leave the other spot blank or fill it in if you want. The metadata document URL is the FederationMetadata.xml
file found in the ACS management portal under "Application integration."
Once you set that up, you may need to adjust your Web.config audience URLs to make everything match what you have in the Azure ACS.