Help With Accessing methods from other classess

Okay I've been given this problem, I'm using software called BlueJ and I think it sucks, I think it sucks because it has a lack of examples of what we need to work, I would like to ask with this program I have, How do I access methods from one class to another, I think this is called polymorphism if I'm correct?

Okay the other class is Called HistogramUI

It has these methods in it
public void setVisible() { }
public void paint(Graphics graphics) { }
private int getHeight(int int0, int int1) { return 0;}
public void setMax(int int0) { }
public void setMedian(double double0) { }
public void setMode(String string) { }
public void setMean(double double0) { }
public void setRollCount(int int0, int int1) { }
How would I call these methods from the class below Histogram?

Any Helps, Hints, Solutions Very needed on this program! Thanks Everyone

public class Histogram
{

public Histogram( long seed )
{

}

/**
* This method needs to call the HistogramUI methods to set up and
* display a Histogram.
*/
public void displayHistogram()
{

}
}

HistogramUI hui = new HistogramUI(...); // Create an instance of the class
hui.<put method name here>; // Call one of its methods

Polymorphism is not the ability to call another object's methods.

Polymorphism is the ability to use one name to call a method or work with an object BUT you don't know exactly which implementation of the method [overriding] or which class or object [inheritance (extends) or interface (implements)] you'll be calling until "run time" - an example of "dynamic late binding" (the time at which a connection is made between caller and callee) which is allowed by Java.