Please note: the folder structure on github is not equivalent with your workspace. To use this source files please download or clone this repository and copy only the tutorial you are working on to your workspace "catkin_ws/src".
The name convention of the files (i.e. tutorial_1) is the status at the end of the respective tutorial (here: tutorial 1).
After copying, go into your workspace with the terminal and type catkin_make.
If you experience any problems with the tutorials, please file an issue in this repository.