Thank y'all for the replies, it is much appreciated!
First, I don't want to seem ungrateful. I apologize for the late reply. This is not normal for me. I just had other matters to attend to that I hope now are over with now...
Newhere: What you directed makes sense to me, but when I tried to follow your directions, I got stuck at the very beginning.
You said: If you want to change the icon of a folder on your desktop, you click on the icon and the (system) icon folder opens.
At this point, I opened the icon, all I get is a blank screen. The window title shows correctly the title of the icon.The menu bar (?) directly under the window title has the commands File, Edit, View, Places, & Help & below that is a blank/empty screen. I'm guessing that I'm in the file manager, Caja?
Then you said: use the 48x48 folder
I fail to see any option to set this...
Sorry if I seem to be a pain, I just don't understand all of this. I didn't go any further since I was lost & afraid to break something.