Download GIMP cuz PS would be hard to find due to the FBI shutting shyt down.
Find a picture you want to place the smilies on. Open both of them separately in Gimp, copy (edit>copy) the smilie, and paste(edit>paste) it onto the other pic.
You may have to do some resizing and erasing to make pics look realistic, but that's basically all you have to do.
To resize a pic in GIMP. Image>Scale Image
The Erase tool is in the Toolbox window, and looks like an eraser.
To move the smilie image around the other picture use the "Move Tool" also in the toolbox, it looks like a arrow cross.
To magnify a picture while working with it use the "Zoom Tool" it looks like a magnifying glass.
GIMP download:
GIMP - Downloads
If you have any questions post it in here.