To write in 3rd person you need to use the words: they, them, it, she, him , her. 
You cannot say I because that means you are talking in 1st person. 
Look at it as if it's like a movie, your watching the movie but your not IN the movie!

Writing in third person means you have to talk about everyone, not just one character, using they, she, he, all, basically you don't have one point of view, you have the general point of view of everyone