In the Print dialog, click the Properties button. That opens the properties dialog supplied by the printer driver (which is different for each printer manufacturer, and sometimes for specific models, so I can't tell you what you'll see there). Somewhere
in that dialog will be a check box for Duplex printing.
Setting the option this way lasts only for the current session. If you print double-sided more often than single-sided, go to the Windows Start menu and click 'Devices and Printers'; right-click your printer's icon and click Printer Properties, and set the
Duplex option there. That will affect all printing from all programs, although you can override it for single sessions through the individual programs.