Simple. Navigate to the login screen of the Google Apps service you would like to access. If you have not yet authenticated or do not have an open Google Apps session you will be asked to enter the username and password. If you have already authenticated you will be directed to the requested service.
Once you enter your username and password Google will recognize that you are a Clearlogin user.
You will then be directed to your login page.
Enter your username, password, and you will be directed to the requested service, ie Gmail, calendar, Drive, etc.