Despite the external difference, the bumper from Citroen C4 Aircross and Peugeot 4008 attached practically the same. The user manual is available here:

How to remove front and rear bumper Peugeot 4008

The attachment of bumpers. The arrows indicate the screws, clips and latches.

Depending on the year of release of the attachment can vary.

Front bumper

the attachment of the front bumper Citroen C4 Aircross

Rear bumper

the attachment of the rear bumper Citroen C4 Aircross