(If you are using NetBeans IDE) Just create a folder in your project but out side of src folder. Named the folder Images. And then put the image into the Images folder and write code below.
// Import ImageIcon
ImageIcon iconLogo = new ImageIcon("Images/YourCompanyLogo.png");
// In init() method write this code
jLabelYourCompanyLogo.setIcon(iconLogo);
Now run your program.