To run this example, you first need to compile the custom source library, which requires headers from OpenMC. A CMakeLists.txt file has been set up for you that will search for OpenMC and build the custom library. To build the source library, you can run:

mkdir build && cd build
OPENMC_ROOT=<path_to_openmc_install> cmake ..
make

After this, you can build the model by running python build_xml.py. In the XML files that are created, you should see a reference to build/libsource.so, the custom source library that was built by CMake. The model is also set up with a mesh tally of the flux, so once you run openmc, you will get a statepoint file with the tally results in it. Running python show_flux.py will pull in the results from the statepoint file and display them. If all worked well, you should see a ring "imprint" as well as a higher flux to the right side (since the custom source has all particles moving in the positive x direction).