Datamax M-Class Operator's Manual page 22

4. Close the Printhead Assembly and press down until it
locks into place.
5. Route the ribbon up and then around to the Ribbon
Take-Up Hub, winding it several times in a clockwise
direction to secure it in place.
6. Close the cover and press the
7. The 'Media Type' setting within the printer's setup must be set to 'Thermal Transfer' to print using a ribbon;
Printers without front display:
Printers with front display:
14
button several times to position the ribbon and ensure proper tracking.
FEED
See section 4.5.2
See section 5.1.2
M-Class