WARNING: This page is about a different car, the 2006 Subaru Baja. However, it is still accessible from the selected car via links, so may be relevant.
Loosen TORX screw (A) and remove the inner rearview mirror.
Fig 1: Locating Inner Rearview Mirror
Courtesy of SUBARU OF AMERICA, INC.
CAUTION:
Be careful not to damage the mirror surface.