computer building - To where on the motherboard (Asus Z87 Pro) do I connect the `+P LED` and `-P LED` wires?

I am connecting my tower (HAF 922) to my motherboard (asus z87 pro) and have a problem with these two 1x1 pins that I believe turn on and off the red LED on the front fan of the tower. My problem is that I am not sure when to connect these:

There is usually a block of connectors on the motherboard that connects to things like the power button, case LEDs, internal speaker, etc.

However, as far as I know, unlike for example USB connector heads, the layout of this block of connectors is not standardized.

So case vendors simply take the two cables (one to "something" and the other back from the same "something") and split them, allowing you to connect them wherever on the motherboard connector block they should go.

I would expect +P LED and -P LED to be the positive and negative leads to the power LED, respectively.

What you need to do is bring out the motherboard manual, look up the connector block (there is usually a diagram showing the relative location of major motherboard components, including that one), and hook the cables up to the proper pins within that block. The exact location of those pins within the connector block will almost certainly be given in the motherboard manual, and is often marked directly on the motherboard as well. They are most likely next to each other, but you cannot always count on that.

Don't worry too much about getting + and - mixed up for LEDs and buttons. If you do, as long as you otherwise connect the wires properly, all that will happen is that the LED won't turn on; the buttons will work just fine regardless of polarity, since in ATX even the power switch is a simple low-voltage closure switch. If the LEDs don't work, just unplug the cables and re-plug them in the reversed positions. Do however make sure you connect them to the correct pins on the connector block.