Use No. 1 to manually resize pictures (drag any corner inwards to shrink picture)
Play with No. 2 to resize pictures by changing the Length by Width settings numerically (enter different numbers thsn the default size revealed).
If your pics won’t post because you get any error msg, take a separate screen shot of the picture, edit as necessary with your regular photo editing on your phone, tablet or computer, the use the icon (no. 3) to post the picture into your ad.