I am trying to use CMake in order to compile opencv.
I am reading the tutorial but can\'t understand what is CMakeLists files and how is it connected to the gui of C
I don't know about Windows (never used it), but on a Linux system you just have to create a build directory (in the top source directory)
mkdir build-dir
go inside it
cd build-dir
then run cmake and point to the parent directory
cmake ..
and finally run make
make
Notice that make and cmake are different programs. cmake is a Makefile generator, and the make utility is governed by a Makefile textual file. See cmake & make wikipedia pages.
NB: On Windows, cmake might operate so could need to be used differently. You'll need to read the documentation (like I did for Linux)