It’s not clear how this is accomplished. We have a catalog with loads of images, that goes to loads of products. Is the only way to get the primary and additional images into a product by adding them manually?
If each image is publicly available with a URL (e.g. in an S3 bucket or a public folder somewhere), then you can import them all using a tool like PowerImporter’s CSV Import. Simply put the URLs in your CSV file and upload it to PowerImporter.
Otherwise, feel free to DM me and I’ll find a way to help.