After you send them the link, your friends will be able to join, provided they have also installed the browser extension and are logged into Netflix. During the playback, there will be a gray Netflix Party box for text chatting. You change your icon and username by clicking the circle at the top by the copy link button.
Unfortunately, at this point you can’t voice or video chat during playback, which could be just fine if your friend group is more into texting anyway.
WIRED: Video chat. Slick interface. Good video quality.