Hi,
First you need to create an instance of your ProgressBar class in the OKButton program, when you have an instance of the ProgressBar class you can call the method.
public void OkButtonPressed() {
...
...
ProgressBar progressBar = new ProgressBar();
progressBar.showTheProgressBar();
...
...
}
You need to adjust the above pseudo code to work with your program, hope this give you a picture.