Lenovo ThinkVision LT2223z 21.5in LCD Monitor - Manual (Page 9)

you can push side volume control key to adjust sound of speaker.
Setting up your monitor
This section provides information to help you set up your monitor.
Connecting and turning on your monitor
N ote:Be sure to read the Safety Information located in the information flyer
before carrying out this procedure.
Power off your computer and all attached devices, and unplug the computer power
cord.
Connect the analog signal cable to the D-SUB connector of the monitor and the
other end on the back of the computer.
Chapter 1. Getting started 1-5