To prevent spamming, accounts that are new to hosting jams must have their jam pages reviewed before they are eligible to appear in the calendar. The page is otherwise fully functional, and you should promote the page as normal. In fact, getting your community to join can help it get reviewed faster.
Although the jam calendar might help bring visibility to your jam, typically a jam with few participants isn’t going to magically pull in a lot of more participants just because it’s on the calendar. You’re competing with limited space for many other jams. So I don’t recommend the jam calendar as your only means of promotion.
Hope that helps