Brother DCP-8020 - Manual (Page 110)

7 - 15 PRINTER DRIVER SETTINGS
Available Options
In order to access the optional 2nd paper tray the option must be
installed in the driver. Highlight the model number from the Available
Options list and click Add. The optional tray will then be listed in the
Installed box, Paper Source Setting list and the screen illustration
will display the 2nd tray.