In order to use a Ada library, you need to make sure that this library is on both your source and object path Search Paths and the Run-Time Library (RTL) and Search Paths for gnatbind. For instance, you can use the library mylib installed in /dir/my_lib_src and /dir/my_lib_obj with the following commands:
$ gnatmake -aI/dir/my_lib_src -aO/dir/my_lib_obj my_appl \ -largs -lmy_lib
This can be simplified down to the following:
$ gnatmake my_appl
when the following conditions are met:
ADA_INCLUDE_PATH, or by the administrator to the file ada_source_path
ADA_OBJECTS_PATH, or by the administrator to the file ada_object_path
Linker_Options, as mentioned in Creating an Ada Library, has been added to the sources.