Adding stickers to your event is a feature exclusive to the virtual booth.

You can do this by going to the "Virtual Booth" section on your event, and selecting either "Beginning" or "After Capture".

In order to add stickers to your event, just click the "Actions" button in the top right corner and select "Manage Virtual Assets" from the drop-down. Then select "Sticker" from the tab and click "Upload".

Tip: To manage and delete stickers you can do this from the management area as well - Event dashboard > Action (drop-down) > Manage Virtual Assets > Sticker.