Making edits to your events, whether it's adding a status update or changing your event's description, is a seamless process whether your event is live or not.
On your event page, click the pencil icon in the upper right corner. This will open the Editordrawer.
The editor drawer opens to the right side of the player, so you can stay engaged in your event while making changes at the same time.
You can review any draft posts.
For example, clicking Event Details gives you the ability to make changes to your title, event time, description and other basic settings while your event is live.
When you are done editing your event, make sure you select Update Settings at the bottom of the Editor. Then click the X in the upper right corner to collapse it.