The package opencl is compatible with built-in CMake targets via CMake v3.6 and prior syntax

    find_package(OpenCL REQUIRED)
    target_link_libraries(main PRIVATE ${OpenCL_LIBRARIES})
    target_include_directories(main PRIVATE ${OpenCL_INCLUDE_DIRS})

and the CMake v3.7 and beyond imported target syntax

    find_package(OpenCL REQUIRED)
    target_link_libraries(main PRIVATE OpenCL::OpenCL)

This package is only an OpenCL SDK. To actually run OpenCL code you also need to install an implementation.

    WINDOWS: implementations typically ship with the drivers of you CPU/GPU vendors.
    LINUX: implementations may be installed from your distro's repo or manually. There are too many to count.
    APPLE: consult your distribution vendor on the state of OpenCL support: https://support.apple.com/en-us/HT202823
