The case connector JFP1 shows two ways depending on whether your case power led plug is a two connection or three but the + connector is clearly at the top of the page. When connecting leds, positive and negative alignment is required but for switches like the power switch or reset its not important since a switch is basically just a break in a single wire thats joined with the switch. You can't do any harm to the computer if you put the plug on backwards but it might not function correctly.
