1. Installing Internal Optional DevicesExpress5800/R120d-2E User’s Guide114Chapter 2 Preparations1.22.2 InstallationFollow steps below to install a power supply unit:1. Refer to steps 1 to 4 in Chapter 2 (1.3 Overview of Installation and Removal) for preparations.2. Remove the blank cover.Important Keep the removed blank cover for future use.3. Insert the power supply unit.until it is locked with clicking sound.