How To Add JPanel With Background Image To Already Setup GUI

I am trying to set a picture in the background of my GUI. I had already made the GUI with the all the required buttons and labels. So I was trying to separately make a class which extends JPanel and add a picture to a panel by overriding the paintComponent() method, and then added it to a frame (I did not set the default layout of the frame, so it was the default...), and it worked very fine. Here is the code:

Java Code:

private BufferedImage image;
public ParentPanel() {
try {
image = ImageIO.read(getClass().getResource("/com/dev_nna/scheduler/UI/1405188.png"));
} catch (IOException ex) {
ex.printStackTrace();

[code]....

Then I needed to add this panel with background picture to the background frame of my already made frame with all the buttons on it.The layout of the parent frame of my GUI was BorderLayout(50, 50), panels (with buttons) were added to it n the north and south positions.

Then I tried to add a JPanel with the background image to the parent frame (of my GUI), (I wanted it to elapse the entire frame, and come under all the buttons and controls, which were only present in the north and south positions of the border layout), and then the panels holding the buttons to the north and south postions of this panel, everything disappeared.

If I don't do anything except adding this panel with the background image to the parent frame, it only takes up the place not taken up by the two panels on the frame (Border Layout)

how to add this panel to the parent frame of my GUI such that it elapses the entire parent frame's background, and the panels containing the buttons should sit on it.

IMPORTANT PARTS OF CODE:-
Java Code:
//TOP LEFT PANEL
JPanel topleftpanel = new JPanel(new FlowLayout(FlowLayout.LEFT, 5, 5));
parentPanel_top.add(topleftpanel);
topleftpanel.setOpaque(false);

[code]....