You can choose to hide a block from your event site, or make it visible only in preview by following these steps:
Go to your event
Click on `Pages` in the menu
Click on `Start` (or the name of your event) next to the house icon
Click on the block that you want to show, hide or be visible only in preview
Scroll down and click on `Show`, `Only in preview` or `Hidden`, depending on what you want to do.