Digital twins, along with Internet of Things and Artificial Intelligence, have been identified as one of the key technologies for Industry 4.0. However, the definition of Digital Twin (DT) is still abstract and context-dependent. In this paper, we present a metamodel that supports concrete and operational descriptions of digital twin deployment. This metamodel encompasses the different aspects of deployment, including the definition of hardware and software components that compose the layered cyber-physical architectures of the digital twin, along with the installation and instantiation tasks that compose deployment processes. Multiple configurations can also be defined to support the deployment of a digital twin in different execution contexts. The relevance of this metamodel was evaluated by two case studies. The first consists in deploying the digital twin of a cobot in a simulation environment. The second applies the approach in a home automation environment. In both cases, our metamodel provides complete and precise descriptions of the deployment process and thus constitutes a viable first step towards a model-driven approach for digital twin deployment.