You have to configure the project build and add the directory where the header file is located. The steps are as below:-
Project > Build options > Search Directories tab
Choose the Policy dropdown list with the option: Prepend target options to project options”
Click the button ‘Add’ to search and add the directory (e.g. ‘include’ directory)
Another popup with the question “Keep this as a relative path?” and click ‘Yes’ to add the directory.