Click the meeting link and Orbit opens the desktop app if it's installed, or offers to join from your browser with no download required. Enter your name, allow camera and microphone access when prompted, and you'll land in the meeting or the waiting room if the host enabled one.
If the host hasn't started the meeting yet, you'll see a waiting screen that updates automatically. Joining by phone is also possible using the dial-in number and meeting ID shown on the invite.