How do I add an experience to "What's new"?
The What's new section is reachable via the left side bar here:
Once there, you are prompted to add an experience from the experiences you have created. If you have not created any experiences, you will be guided to create at least one experience.
Learn more about creating experiences here.
After choosing an experience, then choose a the new version and the former version (or any version). Lastly, "Add experience," and that's it!
The completed experience would be displayed to all users or specific users once they open the app.