If you want to play music in the background during your live event, the easiest way is to play it through your phone, or wired/wireless speakers.
If you want to capture the computer audio directly, you will need to use third-party software like OBS or a physical mixer itself as our platform only supports 1 audio input.
Note: You will need to restart your computer after downloading. You can watch this YouTube video for a quick tutorial. Using OBS and livestreaming at the same time might be too taxing for some computers. The recommended RAM is at least 8GB. OBS is a free third-party software. If you'll encounter issues using it, it's best to check their help page here.