Qt Creator: The Cross-Platform Qt IDE
Qt Creator is a cross-platform integrated development environment (IDE) tailored to the needs of Qt developers. Qt Creator runs on Windows, Linux/X11 and Mac OS X desktop operating systems, and allows developers to create applications for multiple desktop and mobile device platforms.
Necessitas uses a customized version of QtCreator which includes all the required magic to seamlessly integrate Android applications with the C++ world of Qt.
Please refer to the Qt Creator wiki page for download and setup instructions: QtCreator wiki page. Also, please note that Necessitas Qt Creator is part of the Necessitas SDK, so if you have the SDK installed you probably already have everything in place, ready to use!