Actually this is a pretty common problem.
You need to edit the config.txt file. If you insert the MicroSD card into a PC you'll find this file at the root of the SD card. You can edit it with Notepad.
If you're within the Pi OS using SSH or locally, you can find it at /boot/config.txt. You can edit it with Nano.
Change the line hdmi_drive = 1 to hdmi_drive = 2
Reboot if you did this via SSH or locally.