To setup your printer for double-sided printing, first select the Layout option from the Print dialog.
Then, choose Long-Edge binding from the Two-Sided menu. This will enable double-sided printing for this print job only.
To save this as your default setting, you need to create a print options preset. From the Preset menu, choose "Save as..."
Give a name to your new print options preset, for example, “Double Sided.” Then, click OK. This will save all of your currently selected print options as a preset.
Finally, select your new preset from the Preset menu. After printing with this duplex printing preset, it will become the default preset.