how can I start using oop in a real project?

Question

l've read some books and I've wrote a lot of small codes but now I want to go forward and make a real program with a simple GUI.

Answer 1

OOP and GUI are differents.
Object-Oriented Programming
Graphic User Interface

Answer 2

oop has been introduced
to facilitate programming

maybe as you code your gui
you'll find a way to introduce oop

Answer 3

learn a language, learn a few APIs and practice practice practice

Answer 4

thank you for your answers. but l'm asking the next step for a beginner to become a pro. I want something like a tutorial with UML plan for creating a small program. some people suggested mozilla project but I think this kind of projects are too complex for a beginner.