51 43 148 Removing and installing or replacing trim on left or right door pillar (top)

Move front seat upwards.

Release seatbelt screw (1) on front seat and feed out seatbelt strap (2).

Installation: 

Fig 1: Releasing Seatbelt Screw On Front Seat

Courtesy of BMW OF NORTH AMERICA, INC.

Subsequent work is described in: 

Removing panel for door pillar (bottom).