If you use Google Apps, follow these steps:

  1. Open the Safari browser on your phone and go to http://m.google.com
  2. Click on Google Apps user? at the bottom of the screen.
  3. Enter your domain name (e.g., YourDomain.com).
  4. Click the Sync icon in your domain area (this section has a green background).
  5. Sign in if required.
  6. Select your device to configure Calendars.