Hi,
If you are using a VisualGDB-generated Makefile or an MSBuild-based project, simply add the sources of your library to Solution Explorer and adjust the missing include paths (VisualGDB will normally help you discover them and suggest adding them automatically).
Another option would be to import the entire project using our experimental mbed importer, although it may require changes to the open-source importer plugin, as the mbed internal structure keeps on changing between versions.