Dell OptiPlex 5090 Tower Service Manual page 14

Steps
1. Locate the side cover slot on your computer.
2. Align the tabs on the side cover with the slots on the chassis.
3. Slide the side cover towards the front of the computer to install it.
4. Tighten the two thumbscrews (#6-32) to secure the side cover to the computer.
Next steps
1. Follow the procedure in after working inside your computer.
14 Removing and installing components