What it is trying to tell you is that you need to drop in a FOLDER of images, so the five images you have in the resources need to be placed inside a folder, then drag that folder into the gallery.
You can select the five images and then right-click and choose “Folder from Selection”.
not sure if this is a bug or me, thought previously I could select photos then right click and create folder from selection, now I have to select the images then right click on Resources??