The led view will let you adjust each keys LED color (if you keyboard supports it). Up top you see the same thing as the keymap view, but you will notice that each key is a lot more colorful now. The color of the key in this view represents its selected led color. You may also notice that your layers have been changed to only be keys and underglow you can swap between them depending on what LEDs you want to configure.
To change the color of any led you can pick a color in the color picker down below, then select a key you want to change, and push the "Apply" button next to the color picker. To the right of the color picker you will see a grid of colors these are every color currently being used on your board from there you can set them just as if they were a key code eg: drag and drop or click and click. Every time you use a new color in your ledmap this grid will update.