Select "Computer audio" as your audio source in Audio Settings. Selecting "Computer audio" plays all the audio that you hear on your computer. If others are talking, it can cause feedback issues. The best solution to fix this currently is to mute others who are causing echo issues in the left side panel.
Currently using the text chat to talk during a movie is the best in watch parties, however, it is likely that there will be more advanced audio controls for this in the future.
We have a more detailed guide for getting computer audio to work on Mac. You can find it here.
If "Computer Audio" is not working.
First, be sure that you have "Computer Audio" selected as your input, your microphone icon is enabled (no line through it) at the bottom of your party, and that the other members of the party don't have you muted in the left panel.
If none of this works it is likely due to a headset that does not work well with Kast. We recommend trying the 3rd party software VoiceMeeter as a temporary workaround while we look into the issue. Here is a guide on how to set it up
Disclaimer: VoiceMeeter is a 3rd party external tool which we have no control over. Use at your own discretion.