Establishing digital twins is a non-trivial endeavor especially when users face significant challenges in creating them from scratch. Ready availability of re-usable models, data, functions, and tool assets, can help with creation and use of digital twins. A number of frameworks/platforms exist to facilitate creation and use of digital twins. In this paper, we propose such a platform to manage digital twin assets, create composable digital twins from re-usable assets and make the digital twins available as a service to other users. The proposed platform supports the management of re-usable assets, storage, provision of compute infrastructure, communication, monitoring, and execution tasks. Two case studies are used to demonstrate the capabilities of this platform.