Side Retainer

Install the bearing outer race to the differential side retainer.
Install a new oil seal using the ST and a hammer.
ST 18675AA000 DIFFERENTIAL SIDE OIL SEAL INSTALLER

Fig 1: Installing Oil Seal Using ST 18675AA000 Differential Side Oil Seal Installer
Courtesy of SUBARU OF AMERICA, INC.
Apply gear oil to a new O-ring and install.

Fig 2: Identifying O-Ring
Courtesy of SUBARU OF AMERICA, INC.