NOTE: Please read first: Photo size is too big.
Follow the instructions below on how to re-size a photo.
1) Open your selected photo thru MS PAINT (if you are using Windows). Notice the sample photo's size is 5184 x 3456px.
2) Click Resize.
3) Select Pixels. On the Horizontal (width) change the size to allowable size 1200. The Vertical will automatically be 800. Click OK.
4) Notice that the size is changed to 1200 x 800 which is within the allowable size.
5) You may now upload your re-sized photo on your website. And it should look as good as this:
DONE! :)