You always use a Resistor on an LED, unless the voltage is lower than what the LED is rated at, and then it's not going to be as bright as it could, but might work alright, just depends on the LED.
TP1 is the 5v TP spot for the USB connector.
Unless you want your LED to be on all the time and drain the battery, then use the VCC spot from one of the Analog Sticks, it's 2.8v and is switched. If you want a higher switched voltage than that, then you'll have to use an OptoCoupler or Transistor and make one.
If you only want the LED on when it's plugged into a USB port, then use TP1, but use the appropriate Resistor value for a 5v source, plenty of LED Calculators online to use for that.