Ethos means the distinguishing character, beliefs or moral nature of a person, group, or institution.
So you would simply have to write about the person and why you admire them. You would include their beliefs, morals, and character.
For example, if you pick Mother Teresa, you might say when she was born, that she founded the Missionaries of charity, etc. Then you could say you admire her faith in God, her commitment to the poor, etc.