I am just taking a class about critical thinking and I need to make an essay talking about ethics. Can some one explain to me the basic way of a good wrote essay? Thanks for your help

State the premise or gist of your essay in the first paragraph, maybe 1/3 of the page.
Elaborate on your theme for the body of the paper.
Summarize on the last third of the last page.
That's just common sense, but there are no rules.

A good paper doesn't try to cover a broad topic. Ethics is far, far too broad.
You could discuss the differences between morality and ethics, for example.
The two words mean different things to different people.
To me, morality is the province of religions.
To others, it's what is determined locally to be the realm of ethical behavior.
There are dozens of topics about ethics in the realm of science, such as cloning of humans, or genetic manipulation to end certain diseases.
If you work on such a specific topic, be sure to include your definition of ethics as you go.