If you have determined the work you want to use does not fall under the umbrella of fair use, you must obtain permission to use from the copyright owner. There are several ways you can go about obtaining permission.
Once you have identified the copyright owner, you will need to formulate your request. Sometimes a simple email or phone call to the copyright owner may work. If you receive permission over the phone be sure to follow up with a written letter afterwards. Be sure to save records of your permissions.
You can also reach out to the copyright owner by writing a letter. Your letter should include
Click on the link to see a sample request letter.
There is no guarantee the copyright owner will respond to your request. It is at their discretion whether to reply to permission requests. So you may ask, now what can I do to legally use the work?