How do you text ATT phones from computer?

This is from att's website:

: Question:

How do I e-mail a text message to an AT&T wireless phone? ; Answer:

To e-mail a text message to an AT&T wireless phone:

: :# Type the text message as an e-mail through your e-mail account. :#* 10-digit wireless phone number@txt.att.net :# Send the e-mail to the AT&T wireless phone using the following address format for the AT&T wireless phone number: Standard messaging rates apply for the recipient. This information can be found here on their website: https://www.wireless.att.com/support/knowledgeBase.do?content=KB63037.html