Philosophy Ethics

Aristotle/Virtue Ethics:

Here is a prompt for the essay on Aristotle's ethics--essentially all I am looking for is just a detailed explanation of his ethics and this (I would propose) will demand a bit of research on your part.  Please remember to cite any sources you use, and cite them properly.  

Aristotle proposes that happiness is the greatest good for a human life and argues that ethics is essentially the science of achieving happiness. What is his argument and how does he explain "excellence" in human living?