The integral is described in https://github.com/LSSTDESC/N5K/blob/master/README.md and the Levin method was originally proposed here: https://www.sciencedirect.com/science/article/pii/0377042794001189 .
The code is compiled by typing make install. In the main directory there is another makefile for an example main. The documentation can be created via doxygen -g doxyfile followed by doxygen doxyfile . Only standard libraries and the GSL are needed.
For the python module, pip install . (or pip install -e . for a develop install) should do the trick. An up-to-date version of pip (10+) is required.