I am very confused on how to increase the font size in the program of X and O in Tic Tac Toe. Thank you

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.io.*;
import java.util.*;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Image;

import javax.swing.ImageIcon;
public class TicTacToe1 implements ActionListener {

public static void main(String[] args) {
new TicTacToe1();
}



final String VERSION = "Final";

JFrame window = new JFrame("Tic-Tac-Toe " + VERSION);

JMenuBar mnuMain = new JMenuBar();
JMenuItem mnuNewGame = new JMenuItem("NEW GAME"),
mnuInstruction = new JMenuItem("INSTRUCTIONS"),
mnuExit = new JMenuItem("EXIT"),
mnuAbout = new JMenuItem("");

JButton btn1v1 = new JButton("START PvP"),

btnBack = new JButton("< BACK");
JButton btnEmpty[] = new JButton[10];

JPanel pnlNewGame = new JPanel(),
pnlNorth = new JPanel(),
pnlSouth = new JPanel(),
pnlTop = new JPanel(),
pnlBottom = new JPanel(),
pnlPlayingField = new JPanel();
JLabel lblTitle = new JLabel("Tic-Tac-Toe");
JTextArea txtMessage = new JTextArea();

final int winCombo[][] = new int[][] {
{1, 2, 3}, {1, 4, 7}, {1, 5, 9},
{4, 5, 6}, {2, 5, 8}, {3, 5, 7},
{7, 8, 9}, {3, 6, 9}

};
final int X = 700, Y = 700, color1 = 190;
boolean inGame = false;
boolean win = false;
boolean btnEmptyClicked = false;
String message;
int turn = 1;
int wonNumber1 = 1, wonNumber2 = 1, wonNumber3 = 1;

public TicTacToe1() {
window.setSize(X, Y);
window.setLocation(0, 0);
window.setResizable(false);
window.setLayout(new BorderLayout());
window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);


pnlNewGame.setLayout(new GridLayout(2, 1, 2, 10));
pnlNorth.setLayout(new FlowLayout(FlowLayout.CENTER));
pnlSouth.setLayout(new FlowLayout(FlowLayout.CENTER));

pnlNorth.setBackground(new Color(color1, color1-110, color1-100));
pnlSouth.setBackground(new Color(color1, color1-110, color1-100));

pnlTop.setBackground(new Color(color1, color1-110, color1-100));
pnlBottom.setBackground(new Color(color1, color1-110, color1-100));

pnlTop.setLayout(new FlowLayout(FlowLayout.CENTER));
pnlBottom.setLayout(new FlowLayout(FlowLayout.CENTER));
pnlNewGame.setBackground(new Color(color1, color1-110, color1-100));


mnuMain.add(mnuNewGame);
mnuMain.add(mnuInstruction);
mnuMain.add(mnuExit);


pnlNewGame.add(btn1v1);


mnuNewGame.addActionListener(this);
mnuExit.addActionListener(this);
mnuInstruction.addActionListener(this);
btn1v1.addActionListener(this);

btnBack.addActionListener(this);


pnlPlayingField.setLayout(new GridLayout(3, 3, 2, 2));
pnlPlayingField.setBackground(Color.green);
for(int i=1; i<=9; i++) {
btnEmpty[i] = new JButton();
btnEmpty[i].setBackground(new Color(color1, color1-110, color1-100));
btnEmpty[i].addActionListener(this);
pnlPlayingField.add(btnEmpty[i]);
}

pnlNorth.add(mnuMain);
pnlSouth.add(lblTitle);


window.add(pnlNorth, BorderLayout.NORTH);
window.add(pnlSouth, BorderLayout.CENTER);
window.setVisible(true);

}

public void actionPerformed(ActionEvent click) {
Object source = click.getSource();
for(int i=1; i<=9; i++) {
if(source == btnEmpty[i] && turn < 10) {
btnEmptyClicked = true;
if(!(turn % 2 == 0))

btnEmpty[i].setText("X");
else
btnEmpty[i].setText("O");
btnEmpty[i].setEnabled(true);
pnlPlayingField.requestFocus();
turn++;
}
}
if(btnEmptyClicked) {
checkWin();
btnEmptyClicked = false;
}
if(source == mnuNewGame) {
clearPanelSouth();
pnlSouth.setLayout(new GridLayout(2, 1, 2, 5));
pnlTop.add(pnlNewGame);
pnlBottom.add(btnBack);
pnlSouth.add(pnlTop);
pnlSouth.add(pnlBottom);

}
else if(source == btn1v1) {
if(inGame) {
int option = JOptionPane.showConfirmDialog(null, "Quit Current Game?",
"Quit Game?" ,JOptionPane.YES_NO_OPTION);
if(option == JOptionPane.YES_OPTION) {
inGame = false;
}
}
if(!inGame) {
btnEmpty[wonNumber1].setBackground(new Color(color1, color1-110, color1-100));
btnEmpty[wonNumber2].setBackground(new Color(color1, color1-110, color1-100));
btnEmpty[wonNumber3].setBackground(new Color(color1, color1-110, color1-100));
turn = 1;
for(int i=1; i<10; i++) {
btnEmpty[i].setText("");
btnEmpty[i].setEnabled(true);
}
win = false;
showGame();

}
}
else if(source == btn1v1) {

}
else if(source == mnuExit) {
int option = JOptionPane.showConfirmDialog(null, "Are you sure you want to exit?",
"Exit Game" ,JOptionPane.YES_NO_OPTION);
if(option == JOptionPane.YES_OPTION)
System.exit(0);
}
else if(source == mnuInstruction) {
clearPanelSouth();
String message = "";
txtMessage.setBackground(new Color(color1, color1-110, color1-100));
if(source == mnuInstruction) {
message = "Instructions:\n\n" +
"Your goal is to be the first player to get 3 X's or O's in a\n" +
"row. (horizontally, diagonally, or vertically)";
} else {

}
txtMessage.setEditable(false);
txtMessage.setText(message);
pnlSouth.setLayout(new GridLayout(2, 1, 2, 5));
pnlTop.add(txtMessage);
pnlBottom.add(btnBack);
pnlSouth.add(pnlTop);
pnlSouth.add(pnlBottom);
}
else if(source == btnBack) {
if(inGame)
showGame();
else {
clearPanelSouth();
pnlSouth.setLayout(new FlowLayout(FlowLayout.CENTER));
pnlNorth.setVisible(true);
pnlSouth.add(lblTitle);
}
}
pnlSouth.setVisible(false);
pnlSouth.setVisible(true);
}

public void showGame() {
clearPanelSouth();
inGame = true;
pnlSouth.setLayout(new BorderLayout());
pnlSouth.add(pnlPlayingField, BorderLayout.CENTER);
pnlPlayingField.requestFocus();
}

public void checkWin() {
for(int i=0; i<8; i++) {
if(
!btnEmpty[winCombo[i][0]].getText().equals("") &&
btnEmpty[winCombo[i][0]].getText().equals(btnEmpty[winCombo[i][1]].getText()) &&

btnEmpty[winCombo[i][1]].getText().equals(btnEmpty[winCombo[i][2]].getText())

) {
win = true;
wonNumber1 = winCombo[i][0];
wonNumber2 = winCombo[i][1];
wonNumber3 = winCombo[i][2];
btnEmpty[wonNumber1].setBackground(Color.white);
btnEmpty[wonNumber2].setBackground(Color.white);
btnEmpty[wonNumber3].setBackground(Color.white);
break;
}
}
if(win || (!win && turn>9)) {
if(win) {
if(turn % 2 == 0)
message = "X has won!";
else
message = "O has won!";
win = false;
} else if(!win && turn>9) {
message = "Both players have tied!\nBetter luck next time.";
}
JOptionPane.showMessageDialog(null, message);
for(int i=1; i<=9; i++) {
btnEmpty[i].setEnabled(false);
}
}
}

public void clearPanelSouth() {
pnlSouth.remove(lblTitle);
pnlSouth.remove(pnlTop);
pnlSouth.remove(pnlBottom);
pnlSouth.remove(pnlPlayingField);
pnlTop.remove(pnlNewGame);
pnlTop.remove(txtMessage);
pnlBottom.remove(btnBack);
}

}