Yay! I can help you with that, Cindy! (Finally I get to answer a question instead of asking them!)
Here is a pic — the circle is your materials palette and the point of the arrow points to the “add a color” plus sign. If you mess up and have one color two times, the minus sign will get rid of it.
Also showing in the photo are two important things – the Layers Palette (with all the layers you use) and the History (where the undo feature shows!!!)
Usually these three palettes are docked, or “parked” you might say, all together and off to the side, but my PSP is more free wheeling and they just float wherever they’re out of the way.
Here is a nice big picture. I think. LOL!