Prior to adding photos...
..you have to have them a smaller size to begin with. This site has no editing function. Either take photos at a lower resolution, or use editing software to made them no larger than 1200 pixals wide. To resize your photos, I copy them to my computer, then open with GIMP (a free photo editing software) or any other editring spftware. Then resize to less than 1200 pixals wide, save and reload to D4C.