The top right corner of the desktop contains your most frequently used system controls. You're used to this if you're coming from macOS. On Windows, this is like the System Tray that was in the bottom right of your screen.

There's not much to say about the Volume Control. Adjust your system sound by sliding the volume up or down.

If you click on the Settings option, a sound preferences window opens, where you can choose from different alert sounds, and control the volume of any sound devices you have attached to your computer, including the built-in microphone and speakers.