If you've uploaded images that are too small, or need to be replaced for some other reason, there are three ways you can fix the situation.
1) Delete the existing work and replace it with higher resolution image sets. This is easiest, and if you don't have any transcriptions for the work definitely the way to go.
2) Replace individual images in the work with higher resolution images. To do this you'd log in as the project owner, then go to the work's "pages" tab. i.e.:
Then you'd click on the "settings" action to get to a page like this:https://fromthepage.com/
You can replace the image with a larger one in the Page Image field.