Packages OpenCV in a wheel for installation on the RoboRIO.
You can install this on your RoboRIO by installing the robotpy-opencv package
with robotpy-installer (see the docs for details).
For detailed information about how to use OpenCV, see their website. There's lots of documentation and tutorials/etc available.
The image processing section of the Programmer's Guide at the RobotPy documentation site also has some details for using OpenCV on a RoboRIO.