adding a new small picture at the bottom
of a page that has thumbnails (or you can create a new page - we'll do that later),
in an empty space at the bottom,
To add the picture,
first click inside the space where you want the small picture to be,
then at the top of the page, click the dropdown box under "image",
and choose "from my computer"
where you can Navigate to the folder on your computer,
and find the image on your computer (be sure that it's the small picture) that you want to add.
(I identify the small pictures by adding _sm at the end of the name)
When you click on a picture to highlight it,
you will see it on the right side, so you'll know
if it's the one you want.