A good place to start when looking for current copyright status of a work is the Copyright Clearance Center. https://www.copyright.com/ . If a work is protected under copyright (not in the public domain or labeled with a creative commons or other open license), there are limits on how that resource can be used.
Search this website by title, ISBN, or DOI to obtain information about current rights holders for a work. Depending on your intended use of the work, you may need to request permission from the rightsholder before using. Always conduct a fair use analysis of any work before distributing to students or colleagues (via upload or physical copy)
Remember to search the library's holdings for items as well. If the library currently subscribes to the item you need, you can always link out to the content (rather than uploading content to your course or making copies for class).
If you need assistance identifying copyright status, determining if your intended use falls under fair use, or want help requesting permission to use a work, please contact the Library for support.