You can proceed without copyright permission if you are using something that is not copyrightable or is in the public domain. You also don't need permission if you are using it in a way that does not implicate one of the rights of copyright holders or is permitted by a user’s right, such as fair use. If none of these circumstances applies, you need a license to use the work. In some cases, an existing license may cover your use. In others, you will need to get a new license from the copyright holder. For more information on Obtaining Copyright Permissions, check out the University of Michigan Library's excellent guide.
In addition to the copyright issues, it is also vital to follow attribution norms within your discipline. For more information about the distinction between plagiarism and copyright infringement, see below.
Some institutions require you to sign an agreement before accessing their collections. That agreement may limit your ability to use their materials. These agreements are valid even when the materials are in the public domain or using the materials would qualify as fair use. For instance, if you agree to get permission from the institution before publishing any images of items from its collection, you are bound by that agreement.
To avoid trouble on this issue,
Fair use allows certain uses of copyrighted material without permission from the copyright holder. There are four factors to consider when determining whether your use is a fair one. You must consider all the factors, but not all the factors have to favor fair use for the use to be fair. The outline below explains how the fair use factors and their subfactors apply to using third-party material in a dissertation or thesis.
A Creative Commons license makes it easy for you to know how you can use a work. Images licensed under Creative Commons licenses can be particularly useful if you need a generic rather than specific image. Because the rights holder has already given everyone permission to use the image under the terms of the license, you do not need to evaluate fair use or seek permission in order to use it.
When you use a work licensed under one of the Creative Commons licenses, you need to comply with the license requirements (unless your use is otherwise permitted, e.g., by fair use). All Creative Commons licenses require attribution. Using the work without giving attribution means you do not meet the legal conditions of the license. However, the licenses are deliberately flexible about the requirements for that attribution. The Best Practices for Attribution are outlined on the Creative Commons wiki.
Copyright infringement and plagiarism are related but distinct concepts. Plagiarism is using the work of another without attribution. Copyright infringement is any reproduction, distribution, modification, performance, or display of a copyrighted work without the permission of the rights holder that does not fall under fair use or another user's right.
It is possible to plagiarize even when you have cleared permission for all the copyrighted works. Similarly, it is possible to infringe copyright even when you have given careful attribution. In addition to resolving the copyright issues, you must follow attribution norms within your discipline in order to avoid plagiarizing others' work.
U.S. copyright law does not require citation in a particular form. However, following academic citation norms can help improve your fair use analysis. Check with your advisor for help figuring out what citation style you should use in your dissertation.