Select the Send a Text Message option from the page
Enter the AT&T recipient's wireless phone number in the To: field. Only one phone number may be entered at a time. You don't have to enter dashes as they will be automatically entered for you.
Enter a message in the Message: field. There is a limit of 150 characters.
Click on Send.
If the message was sent successfully to the AT&T customer, you will see the following message at the top of the screen: Your message has been submitted for delivery.Standard messaging rates apply for the recipient.
Note: If the following message is displayed after you click the Send button: Your message could not be delivered because of the following problems. The phone number you entered in the "To" field is not a valid AT&T wireless number, then your message will not be delivered because the phone number in the To: field is not a valid AT&T wireless phone number. Messages cannot be sent to former AT&T Wireless customers using myWireless Account.