Finding FITS files
When you download a FITS files (from anywhere), the default filename is very likely related to the process id on the server, e.g., it won't mean anything to you 10 minutes after you download it. In the process of downloading images, you should rename the images straightaway to be something that you can understand and remember later on.
Most coherent, developed, tested materials
Finding images using Skyview -- Dr. Luisa Rebull (2020) but developed over 10 years