If fair use will not suffice, you will need to seek a license.
A license is a permission and, in this context, means the same thing:
The terms “license” and “permission agreement” are often used interchangeably. You may also find that, in some situations, a license or permission agreement is referred to as a “clearance agreement.” “Clearance” is a general term used to describe the process by which permission is granted. From Stanford Libraries.
First, if the material is still under copyright (in other words, not in the public domain), you must figure out the copyright holder, which is sometimes easier said than done. It can often be hard to know just who to contact, as sometimes the rightsholder is no longer the author, or their contact information is hard to track down.
