Hi Len
Just load your picture into ‘Photoshop’ or similar program, Select ‘Image Size’ and set to 100w x 120h. This will shrink the image and just re-save as a Jpeg. Opt out of the paint prog, find your new image, right click and select properties to confirm size. If ok just upload.
I don’t know why the instructions say 100 x 120, as if you look at all the other pictures, including Vinnies (photograph) they are only 50 x 60 !
Cheers Ken