When including header files into your project, the compiler must be told which directories must be searched to find those files. To do this:
- Open the Project properties. There are a number of ways of doing this. For example, make sure the Project is highlighted in the Project Explorer view then open the menu "Project -> Properties".
- In the left-hand list of the Properties window, open "C/C++ Build" and select "Settings" and then the "Tool Settings" tab.
- In the right-hand pane, choose the "Includes" section under the "MCU C Compiler" or "MCU C++ Compiler" group, and click on the "Add" icon.
- Now add each of the directories that you want the compiler to search to find your include files