WARNING: This page is about a different car, the 2014 Subaru Forester. However, it is still accessible from the selected car via links, so may be relevant.
Install each part in the reverse order of removal.
NOTE:
Assemble the trim panel - center pillar LWR to the trim panel - center pillar UPR securely.
Fig 1: Installing Center Pillar LWR Trim Panel To Trim Panel