Using the 10mm allen, you turn that bolt counterclockwise. They are tight.
DO NOT use the steering wheel lock to hold the wheel against the force of turning the bolt, try using a helper to hold the wheel while you turn the bolt. They are a bear to turn, but once you break it free, it's a snap.
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72
'02 CLK320 Cabriolet - wifey's mid-life crisis
2012 VW Jetta Sportwagon TDI...at least its a diesel
Non illegitemae carborundum.