As of my last knowledge update in January 2022, HBO Party did not have a built-in "party" feature similar to some other streaming platforms. However, things have changed since then.
If HBO Max has introduced a party feature or if you're referring to a third-party extension or service that enables synchronous watching with friends, the steps could vary. Here are general steps you might follow:

• Check for Updates: Ensure you have the latest version of HBO Max installed. Check the app store on your device for any updates.
• Explore Features: Open the HBO Max app or visit the website and explore the available features. Look for any social or watch party options within the app or website.
• Third-Party Services: If HBO Max doesn't have a built-in party feature, there might be third-party services or browser extensions that allow you to sync your viewing with friends. Some extensions work with various streaming services, including HBO Max.
• Coordinate with Friends: If you're using a third-party service, coordinate with your friends to ensure everyone has installed the necessary extension or app and understands how to use it.
• Start the Party: Once you've found a suitable method, initiate or join a party according to the instructions provided by the platform or extension.

Please note that since my information is not up-to-date, changes or new features might be introduced after January 2022. Check the official HBO Max website or contact their support for the most accurate and recent information on any watch party features they may have implemented.