The address book is a great place to store the e-mail addresses
you use so you don't have to type them over and over.

To enter names in the address book:

1. On the Windows menu, choose Address Book.
2. Click New User on the toolbar.
3. Enter the information in the fields. Tab to move from field
to field.
4. Click Save.

Now all you need to do is type the first few letters of the
person’s first name in the To:, CC: or BCC: field of the message,
and their name will automatically appear.  Once their name
appears, press the comma key to move to the end of their
name and begin typing the next name.

We realize that you have about a billion addresses already
entered in another e-mail application. We can import Address
Books from Netscape Navigator, Claris Emailer and Eudora Pro.
For more information on importing, choose Help from the 
Apple menu, and then click Work with the Address Book.

For more information, choose Internet Mail and News
Help from the Help menu.