It's easy! And we made a quick video recording to show you how at https://cl.ly/c397a0680ff2.
For reference, you can add dates by:
Step 1: Going to the "Basics" tab of the Journey Creator tool and scrolling to toggle on the "Specific Dates" button
Step 2: Scroll to the bottom of the page where you'll find the question "Select your Experience Start Date".
Step 3: Click on as many calendar dates as you'd like. Each date you select will add a scheduled departure of that experience to the journey's public page.