The design and integration of the propulsion system is known to be an interesting, multi-disciplinary challenge in aircraft design projects. Especially for new aircraft configurations, it is important to gain a lot of knowledge in the preliminary design stages. An example of such an unconventional configuration is the box-wing aircraft examined by the PARSIFAL project. Therefore, a Knowledge Based Engineering approach towards engine design and integration is developed in this thesis. This new approach allows to consider the propulsion discipline in multi-disciplinary design and analysis routines. By employing the ParaPy software, the complete aircraft geometry can be created and subsequently subjected to aerodynamic analyses in VSAERO. The developed tools are validated and employed to explore the design space offered by a closed-wing arrangement. Based on this exploration, a turbofan system and installation location are recommended for the PARSIFAL aircraft.