Open Gmail and sign in to your account
Click the Google Apps menu and open Contacts
In Google Contacts, click Create label
Enter a name for the group and save it
Select the contacts you want to add to the group
Click the Labels icon
Choose the label you created
Open Gmail and click Compose
In the To, Cc, or Bcc field, type the group label name
Select the group from the suggestions
Send the email to the group