We recommend first reading this guide: Inserting Widgets into Shopify
If you are looking to select or edit the artwork image that your widget is taking from your product page, this guide will take you through the steps to identify where to modify it to the right image.
STEP BY STEP
1) Once on your Shopify site, search for the ArtPlacer app. In your installed Widgets, look for the one you want to edit.
2) Go to the Select Image Position option
3) Select the number that corresponds to the position of your product. For example, if the image of your artwork appears first, then you should select 1. If the image of your artwork appears second on your product page images, then you should select 2.