how do i do this?

Write the class declaration for class Square that has a private instance variable side of type double and a no-argument constructor that sets the side to 1.0 by calling a method named setSide

First thing you do is pay attention in class. Everything you need to complete this assignment was covered by your teacher. Read your notes. Read your textbook. Read online tutorials. Once you have done that attempt to write the code. If/When you have problems come back here, post your code and ask a specific question.