OER is easy to use, but can be overwhelming because OER includes a variety of resources without specific qualifications of what it is or isn't. There are many tools that are open and freely available that are not meant for educational purposes but can be used in the classroom. On the other hand, there are resources that claim to be OER but have hidden costs to the user. Although, OER is not necessarily free, as creators and users we use our time and resources at our disposal that are not free, OER are free for users to use.
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.