It is suggested to add images 5-8 at a time. This way you can just copy and paste the "DUPLICATE-THIS" Grid.
*Click on the green area and copy/paste with shortcuts without clicking another area. CMD(ctrl) + C and then CMD(ctrl) +V.
After you have duplicated the grid, double click on the image, and click replace. This is the area where all your uploaded images are.
if you would like to add more images, duplicate an existing one and double click to replace it. You can also click and drag images around by making sure they are inside of the "Div Block" within the Grid "DUPLICATE-THIS".