1. Select the Gallery that you want to add or update the image to, then click Manage Gallery from the Gallery settings panel.
2. Here you can either Click Add Images or Clear all Images.
3. To change an Images, click the image that you want to change and then select the image from the folder that will appear. You will need to click the X to return to the Manage Gallery Items menus.
Please remember to click Save when you are done.