Just like skipping to the next song on your CD player, click this icon (always at the bottom of the gallery screen) to advance to the next point on the guided tour.
To see or read more about an item, click it. A window will appear with an image or text.
When you see this icon in a window, click it to make that window as large as possible. Use your mouse to scroll through text.
Whenever you see an “X” in the upper-right corner of a window, click it to close that window.