Authenticate to web site from Win 8 App?

I have a Azure web site.  In it, I'm using Azure Active Directory to do authentication.  Here's a section of the web.config to illustrate what is in place:

<system.identityModel>    <identityConfiguration>      <issuerNameRegistry type="System.IdentityModel.Tokens.ConfigurationBasedIssuerNameRegistry, System.IdentityModel, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"><trustedIssuers>          <add thumbprint="____" name="https://____.accesscontrol.windows.net/" /></trustedIssuers>      </issuerNameRegistry>      <certificateValidation certificateValidationMode="None" /></identityConfiguration>  </system.identityModel>  <system.identityModel.services>  <federationConfiguration>      <cookieHandler requireSsl="false" />      <wsFederation passiveRedirectEnabled="true" issuer="https://_____.accesscontrol.windows.net/v2/wsfederation" realm="_____" requireHttps="false" /></federationConfiguration>  
</system.identityModel.services>

The web site is working fine, and authentication works as desired.

Now, I want my Windows 8 App to access content via URLs on this web site, and I need the App to authenticate too.

All the examples I have found deal with using Mobile Services, but I already have a web site and I need the App to authenticate with the web site.

Are there any documents or examples that show how to do this?

Thanks,
Glen