That's what I used
#include <Keyboard.h>
void setup() {
// make pin 2 an input and turn on the
// pullup resistor so it goes high unless
// connected to ground:
pinMode(2, INPUT_PULLUP);
pinMode(3, INPUT_PULLUP);
Keyboard.begin();
}
void loop() {
//if the button on pin 2 is pressed
if(digitalRead(2)==LOW){
//Send the message
Keyboard.print("Hello!");
delay(1500);
}
//if the button on pin 3 is pressed
if(digitalRead(3)==LOW){
//Send the message
Keyboard.print("World!");
delay(1500); }
}