A quick run-through of the BIOS update process.
If the computer has bitlocker enabled, turn if off! A BIOS update is enough of a change to the machine that bitlocker will freak out and lock the drive.
Find the newest version of the BIOS for the specific make and model of machine you intend to update on the Dell website. The A23 bios for an optiplex 9020 is very different from the A23 for an optiplex 7050. Make sure to only flash update the BIOS with the approved file.
Download the appropriate file, and move it onto the BIOS stick you plan to use. There are multiple floating around through the office, but at least one should be at the imaging station.
Shut down the machine you plan on updating, insert the stick, and boot the machine, pressing "f12" until you get to the boot options screen. Choose "flash bios update". Navigate to the file you just put on the flash drive, and run it. This will overwrite the existing BIOS, so it is important to not interrupt the process.
The computer will restart after the flash update is finished. If you press "f12" during boot to go to the BIOS setup screen, the version number should now be whatever you updated it to!
If you had to disable bitlocker, please remember to re-enable it!