Most OERs have a Creative Commons license on them. Creative Commons (CC) licenses allow the creator of a work to change the copyright from "all rights reserved" to "some rights reserved". There are a variety of CC licenses authors can choose from and they can be mixed and matched as needed. Most of the licenses require users to provide credit to the original creator. Some licenses specify that you can remix and reuse, but not for commercial purposes. The Creative Commons website has more useful information about license specifics. (creativecommons.org/share-your-work/)
To download images to add to your work see the Creative Commons downloads website. (https://creativecommons.org/about/downloads)
Within the bounds of Creative Commons licensing there are 5 key points to consider when using OERs:
OERs include a wide range of materials such as: assessments, assignments, books, case studies, courses, journals, primary sources, reference materials, simulations, tutorials, tests, and textbooks.
Defining the "Open" in Open Content and Open Educational Resources was written by David Wiley and published freely under a Creative Commons Attribution 4.0 license at http://opencontent.org/definition/.
This is a educational video from New Zealand is about how to share downloaded digital content legally using Creative Commons licenses.