To download image files from your experience, you need to first download the CSV file.
To do this, go to the setup of your experience and then navigate to the "Download" tab.
Note: You may not be able to see this tab dependent on your corporate policy.
This screen gives you some options on the submissions that you would like to download. You can edit the time period you would like to download from (if you leave those fields blank, it will download submissions from the entire length of the gallery), and edit these other fields. Then click "Download File."
Once you download the file, open it with any excel software. You will then see a column with the label you've given to the image upload field. In this column, there are links to the image that you can follow and download the image from there.
Pro Tip: In the URL change the word "large" to "xl" to get the full resolution version of the image.