Javafx Addition

I recently started using Javafx and I'm very new to it I am trying a create a program where once you enter all the code and run it a small box appears asking you to enter number 1 and number 2 and then the program sums up both of those numbers and print the result in the result tab. I am getting stuck on where you have to write a code in order for you to press the button to calculate the number and where you need to add both of number.
Thanks

import java.math.BigInteger;
import javafx.fxml.FXML;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.event.ActionEvent;
import javafx.scene.control.TextField;

public class AdditionAppController {

@FXML
private Label Number1Label;

@FXML
private Label Number2Label;

@FXML
private Label ResultLabel;

@FXML
private TextField Number1TextField;

@FXML
private TextField Number2TextField;

@FXML
private TextField ResultTextField;

@FXML
private Button CalculateButtonPressed;

@FXML
void CalculateButtonPressed(ActionEvent event) {
    try {
        BigInteger Number1 = new BigInteger(Number1TextField.getText());
        BigInteger Number2 = new BigInteger(Number2TextField.getText());
        BigInteger result = Number1.add(Number2);

        //ResultTextField.setText(Integer.(result));
    } catch (NumberFormatException ex) {
        Number1TextField.setText("Enter first number");
        Number1TextField.selectAll();
        Number1TextField.requestFocus();
        Number2TextField.setText("Enter second number");
        Number2TextField.selectAll();
        Number2TextField.requestFocus();
    }
}

    }

You need to add an event handler to your CalculateButtonPressed.

If you're using Scene Builder, what you would do is click on the "Calculate Button", and on the right hand side collapse all the other sections and expand the "Code" section.

so in fx:id you would set the ID to CalculateButtonPressed, and "OnAction" to something like "onCalculateButtonPressed".

Then go back to your code and add an event handler from FXML like so:

    @FXML 
    void onCalculateButtonPressed(ActionEvent event) {
       //Add your code to calculate your sum here
    }

Fun feature of Scene Builder, you can copy some skeleton code if you go to View > Show Sample Controller Skeleton and it will generate it for you. You can copy and paste parts of it (or all of it) into your own controller.

If you're NOT using SceneBuilder, in your fxml add to the component fx:id="" and onAction="#actionHere" so yours would be:

<Button fx:id="CalculateButtonPressed" onAction="#onCalculateButtonPressed" text=... />

And you would still add the same event handler code that I posted above.