No matter what you hear,"fair use" is not a grant of permission to use a quantity of someone else's copyrighted material. "Fair use" is a defense for when that person sues you for copyright infringement. There is no way of knowing in advance if you are going to be able to successfully defend your use of someone else's copyrighted material on that basis. The threshold for asserting the defense, however, is that you are using the copyrighted material in a work of criticism, comment, news reporting, teaching, scholarship and/or research. [Section 107 of the US Copyright Act]
This post is not intended as legal advice to any person.