In order to replace one of the 4 default icons, go to your Apps, hold down an icon and drag it to one of your 4 spots instead of dragging it to a spot in one of your 7 panels. The icon you replace will glow blue while hovering.
Enjoy #1.
If you want 3, 2, or only 1 icon in the 4 panel thingy; go to your apps; hit the left "square in square" button at the bottom; hit "Manage apps"; then press, hold, and drag/drop it anywhere up out of the box.
Enjoy #2.
If there is proper nomenclature for all of these procedures, please correct me. I'm new (6 days) to this Android thing.