First of all open Outlook and choose the option of file from the top of the menu.
Then, on the left side of the menu, choose the option of information to continue.
Choose the option of add account from the screen that displays in the next tab.
After that, Enter necessary information such as your name, email address, and mail password in the text field.
Enter the button of next. Then enter the button of finish.
Read more here:- https://datarecovo.puzl.com/_news/How-do-I-Add-My-ATT-net-Email-to-Outlook%253F/302375
See Also this post:- http://datarecovo.populr.me/how-to-setup-att-email-on-outlook-mail