Use Other People's Work
Copyright law specifies many limitations and exceptions to the copyright owner’s exclusive rights, most notably fair use. If the right to use someone else’s copyrighted work in a particular way is not granted by an exception or limitation in copyright law or a licensing agreement, you must acquire written permission for the use, either through a licensing agency or directly from the copyright owner. Alternatively you could find another work to use, for example, a work in the public domain (copyright expired).
The Fair Use Policy of Carnegie Mellon University explains what copyright law allows you to do with other people’s copyrighted material. The Appendix to the Policy provides information to help you conduct an analysis to determine if a proposed use is a fair use. For more information, see Using other people’s copyrighted work.