Would I simply run a wire from the + side of the power supply, put a resistor inline (same value as R20 from the PSU spec, 4.7k-10k?), then the LED, then run a wire back to the - side?
Yes, the resistor can be anywhere in series, and the LED anode must be toward the positive
power supply terminal. LEDs are easily damaged by connecting in reverse polarity over 5VDC.
power supply terminal. LEDs are easily damaged by connecting in reverse polarity over 5VDC.
The entire resistor and its solder joints to the wires can be covered in heat-shrink for a neat insulated arrangement inline.