Using Google Apps on your Android phone

(Source Google Administrative Help center)

Your Android device is easy to setup for Google Apps email, contacts, and calendar access. Here's how to set it up:

1. Open the Accounts & Sync Settings screen on your phone. You can do this in Contacts by pressing Menu and touching Accounts, or directly in the Settings application.
   
   
2. The Accounts & Sync Settings screen displays your current sync settings and a list of your current accounts.
3. Touch Add account.
4. Touch Google to add your Google Apps account.
5. Touch Sign in when prompted for your Google Account.
6. Enter your full Google Apps email address as your username, and then enter your password.
7. Select which services you'd like to sync.