Install the trim on the side panel

Check if clamps (1) and the mounts of clamps (1) are available and check them for damage
Damaged or missing clamps (1) must be replaced

If the mounts are damaged, trim (2) must be replaced

Courtesy of BMW OF NORTH AMERICA, INC.
Guide the trim (1) at the side panel forward and engage it at the clamps (2)

Courtesy of BMW OF NORTH AMERICA, INC.