The ITER Project is currently in its construction phase. All plant systems required for the first plasma phase, including captive components in the Tokamak Complex buildings, are being installed. The main activities of this construction phase are in the Tokamak and Diagnostic building, now that the civil structure of the Tritium building roof is finalized. In order to launch the construction phase of the plant systems, the engineering has to be completed and documentation compiled in the form of engineering work packages (EWPs). These EWPs need to be approved, in line with the construction schedule, and must then be provided to the construction contractor for them to prepare the detailed installation work packages (IWPs). The material has to be made available and the manufacturing of the systems, structures, and components (SSCs) has to be completed, according to the requirements, as defined in the technical specifications. The Tokamak Complex as a facility has to be managed accordingly, to allow the construction of multiple building openings and penetrations. Installation of piping and mechanical systems, as well as electrical instrumentation and control (I&C) and cable pulling can then take place. This article describes the handover from engineering to the construction domain, utilizing the "EWP Toolbox" in order to provide the required content in the EWPs. The simplifications implemented in the document production have resulted in an overall cost reduction. This demonstrates that processes must be as simple as possible, providing the necessary documentation at an appropriate level of information and quality. The process of material procurement, on-time, for a large-scale project is described with the mitigation categories herein defined. The constraints to be considered in the construction phase are also described, along with the daily management of the facility and the environmental conditions that must be respected for the Tokamak machine assembly. Due to the sheer size and scale of the ITER project, these aspects can all be considered unique. The effectiveness of the visual management and the coordination of operations are, in the context of an international project such as ITER, described with "Lessons Learned" up to the construction phase provided. This article is concluded with a summary of the current status of the construction phase in the Tokamak Complex with some figures relating to the various building levels.