OER allows creators to make and own their creation with the condition that it can be used by others without limitations. The user can adapt, modify, and improve on another's OER and can combine them. Then, they generally share their modified resource with others.
OER can be used for individual items at a micro scale, such as an assignment, or they can be used to develop an entire course or curriculum.
There are several good research guides created at other institutions that can guide you through the process based on your needs.