To write a new message, click the Compose Mail link on any Gmail screen (it's on the left, under your school Apps logo).
Enter your recipient's email address. You can type the address in the 'To:' field, and Apps mail will automatically suggest addresses from your Contacts list. Hit Enter to choose the name at the top of the list, or scroll down to choose a different address. If Apps mail doesn't suggest the address you want, just continue typing.
Note: Apps mail will first suggest the addresses you send mail to most often. To view a complete list of your most frequently mailed contacts, click Contacts on the left side any Apps mail page, then click Most Contacted.
You can also choose the address in your Contacts list by clicking the 'To:' link just below the Send button. This will open your Contacts list and allow you to select one or more recipients.
Enter a subject for your message in the 'Subject:' field.
Write your message! Just click in the large field and type away.
When you're done composing, click the Send button (located just above the 'To:' field). You'll see a confirmation at the top of the window that your message was sent.
You can delegate access to your Gmail to another person so they can read, send, and delete messages on your behalf. For example, you can delegate e-mail rights to an admin in your school. The delegate can also access the other person's contacts by clicking the Contacts link. Clicking the To, Cc, or Bcc links in the mail compose window will also bring up your contacts.