(See attatched image)

Turn the printer off.

Right click on the printer driver, and select Properties, then go to the Device Settings Tab.  You'll see a screen like the one below...

Set yours like this one, with DT Media with gap selected.

Click Apply, then go to the General Tab.

Turn on the printer.

Then on the General Tab hit "Print Test Page". 

Once the test page is finished, turn the printer off.  Then calibrate the printer by holding down the feed button while powering the printer on.

Once the printer is finished calibrating, your printer will be in Direct Thermal mode.