Lenovo ThinkCentre M55e - Manual (Page 30)

2. While holding the rear of the computer chassis down, pull upward on the
handle provided to remove the PCI riser assembly and any adapters that are
currently installed.
3. Pivot the drive bay assembly upward to gain access to the system board.
4. Locate the memory connectors. See “Identifying parts on the system board” on
page 4.
22 Hardware Replacement Guide