If you want to add images into the images folder within the WebSpawner builder, you can drag and drop them. You can also copy and paste. Then they will have them easily at your disposal when you need them. If you're going to use images more than once.
If you figure you're going to use a certain image more than once, you are going to want to load that into your archive in the builder.
Go to the right-hand menu and click Modules. You go tot he second category, "Images and Video," and there will be three icons there. The second icon across is "Image" and that is what you will drag onto the page.
You'll be confronted with a dialog box that says "Add Image." When you click "Select Image" you will have another box that will present you with the images you may have in your builder already,. If you don't have any, you can click the "Upload Images" button that is in front of you, or you can go to a directory on your computer where images are located and drag and drop them into the builder yourself. Either way it works, and then from there it is easy to insert the images onto the page of your WebSpawner site and continue to edit.