Hi Megan,
You need an adapter from your dealer which attaches to the TDC6, the part details are:
Trimble TDC6 Device Bracket with Magnetic Plate
Part number:125521-GEO
The mount simply clips to the TDC6 and once attached the device can be attached to the handle in either orientation. I've taken a pic from a similar position to yours:
Regards,
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Mark Kellaway
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