First-person immediately puts the reader inside the narrator's head, which allows for an intimate portrayal of thoughts and emotions. You can effectively communicate how each moment feels—delivering sight, sound, smell, taste, and touch—through the prism of your narrator.
You should write about what the person did/does in their life and how it affected the world and/or themselves and/or people around them. You could also include their relatives, family members, siblings, hobbies, etc.
It is the choice or arrangement of words