For every event that you create in the app, corresponding product will be created in your store. You can manage your product from your store where you can add images to the event that you have created.
1. From the left navigation bar, select the option Products. You will see list off all the events that you have created in the Servv.
2. Select the event where you want to add the image. In the Media section, add the image from your system then click on save. The image will be added to your event.
3. Go to your website and check for the event. You will see the event will appear with the added image.
Other articles to refer to for information on events within the store space:
View Products and Orders for the events.
How to move your event product to separate collection?
How to only allow people who have purchased a certain product to book an appointment?