How can we make the visual part to code. And how do we hook it up to the code?

Answer 1

Are you talking about Graphical User Interface?
If so, research Swing (The official Java GUI toolkit). Try creating a few dialog box programs. Download IntelliJ Idea and try out their Graphical GUI designer if you so wish. Good luck - the transition from console to GUI is always fun and exciting!
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Answer 2

If ur starting go with JavaFX (FXML, Gluon Scene Builder), I think it should be easier and its successor of Swing.
U can also code GUI manualy in JavaFX if u want...