This is my sketch for one button/ one relay:
const int buttonPin = 2;
const int relPin = 13;
int buttonState = 0;
void setup() {
pinMode(relPin, OUTPUT);
pinMode(buttonPin, INPUT);
}
void loop() {
buttonState = digitalRead(buttonPin);
if (buttonState == HIGH) {
digitalWrite(relPin, HIGH);
} else {
digitalWrite(relPin, LOW);
}
}