You can provision apps under Google Cloud Identity through the following steps:
Login into Google Admin Console
Click on the left side bar menu and select the Apps option then select SAML apps
Click on Add a service/App to your domain
Search an app under the search bar and follow the instructions provided
Note: There will be information provided under this screen that will be used to provision on the app's side.
Your users will now be able to use Google Cloud Identity to log into the app you set-up