Begin by reading the question closely and making sure you understand it. Specifically this means that you should know what methods and constructors your class will have including the types of their arguments and, for methods, the type they return. Additionally you should know what each method or constructor is supposed to do - it's a good idea to indicate this with a javadoc comment (probably just a sentence) accompanying each method and constructor.
Once you know what you are doing you can begin to implement each of the methods and constructors. At this point you might find it useful to have a main() method (possibly in another class) which tests each method and constructor to ensure that it does what it is documented to do.
I doubt whether anyone is going to write your code for you. But if you are unsure about what the question means, post the skeletal code indicated above and someone is sure to say if they think you have left something out, or misinterpreted the intent of the question.
If, having implemented a method or constructor, you find that it doesn't perform exactly as documented, again post your code so you have a specific question that can be addressed.