An Author is a person who writes books, movie scripts, and other things. Authors may write original work or may adapt other people's work. There's no problem about adapting other work provided you respect Copyright and give a reference.
If you're writing for School, College or University your teachers or lecturers will want you to write a great deal yourself so you learn how to write. A few referenced quotes should be OK. If you're unsure ask teachers or lecturers how much you should write yourself.