Linking Header File with Main.Cpp file in Codeblocks

I am trying to use codeblocks to compile the code available here

The thing is every time I try to build and run, I run into the following error:

|/.../head_pose_estimation/opencv2/core/core.hpp|48|fatal error: opencv2/core.hpp: No such file or directory

Does anyone know how I can fix this? Thank you!