When you organize an online event, Watch Stream page is where you could share your online viewing URL and instructions on how to join your event with your attendees. Watch Stream page will be automatically enabled when you set your event page to "Online event".
Users who ordered tickets for your event will gain access to the Watch Stream page for the event through ticket dashboard in their account, the order confirmation email as well as the event reminder email (sent automatically 24 hours before the start of the event). Users will need to login to the account they used to order their tickets to access the Watch Stream page, and users who didn't purchase tickets cannot access the Watch Stream page for your event.
If you do not wish to share the online viewing URL on Watch Stream page, it is still important to add notes on Watch Stream page to let your attendees know how they can join your event. Please see Creating an event page for an online event for more information on how to register the Streaming URL and notes on the Watch Stream page of your event.