1. LED & Resistor

void setup() {
  // put your setup code here, to run once:
}
void loop() {
  // put your main code here, to run repeatedly:
}

Ohm's Law

Resistance = Voltage ÷ Ampere

Ω = V ÷ A

Arduino output 5 V

LED requires 2 V, 0.02 A

Minimum Resistance = 150 Ω

150Ohm Resistor with 1% tolerance.