You don't. A JTextField is meant to only show one line. To show multiple lines, use a non-editable JTextArea or perhaps even a JLabel. For the JLabel you would need to wrap the contents in HTML so you can use line breaks. For instance:
(without the HTML pieces, everything will be shown on one line)
Perhaps even better is to use a JPanel with a GridLayout where you put in 4 JLabels with the 4 values.
Okay. It worked. Thank you. But I have another question. Since this is an address book program, for example after I type in Name : John, Admin No: 20, Phone No: 123, Email: abc and these information will be shown in the jtextarea, how do I put another information in the same jtextarea without clearing this existing John information?