Install and open the Xbox app on your PC
Sign in with the same Microsoft account used on Xbox
Open the Friends or Party section in the Xbox app
Join a party invite if you received one
If the party is from a friend, open their profile and select Join Party
Make sure your microphone and headset are connected
Allow the Xbox app access to your microphone in Windows settings
If needed, install the Xbox Game Bar and open it with Win + G
Use the Party chat widget in Game Bar to join or start a party
Check that your PC and Xbox app are updated
Make sure cross-platform party chat is supported for the game or party you want to join