Basic program for your micro:bit to control LED and read push button state using Arduino IDE.

MicrobitLEDButton.ino

const int COL1 = 3; // Column #1 control
const int LED = 26; // 'row 1' led

const int BUTTON_A = 5; // The number of the pushbutton pin
const int BUTTON_B = 11; // The number of the pushbutton pin

long previousMillis = 0;
long currentMillis = 0;
int interval = 500;
boolean ledState = false;
boolean buttonAPressed = false;
boolean buttonBPressed = false;

void setup()
{
  Serial.begin(9600);

  Serial.println("microbit is ready!");

  pinMode(BUTTON_A, INPUT);  
  pinMode(BUTTON_B, INPUT);   

  // Because the LEDs are multiplexed,
  // we must ground the opposite side of the LED
  pinMode(COL1, OUTPUT);
  digitalWrite(COL1, LOW);

  pinMode(LED, OUTPUT);
}

void loop()
{
  currentMillis = millis();
  if (currentMillis - previousMillis > interval) {
    previousMillis = currentMillis;

    ledState = !ledState;
    digitalWrite(LED, ledState);
  }
  
  if (digitalRead(BUTTON_A) == LOW &&
      buttonAPressed == false) {
    buttonAPressed = true;

    Serial.println("Button A is pressed.");
  }
  else if (digitalRead(BUTTON_A) == HIGH &&
      buttonAPressed == true) {
    buttonAPressed = false;
  }

  if (digitalRead(BUTTON_B) == LOW &&
      buttonBPressed == false) {
    buttonBPressed = true;

    Serial.println("Button B is pressed.");
  }
  else if (digitalRead(BUTTON_B) == HIGH &&
      buttonBPressed == true) {
    buttonBPressed = false;
  }
}