The Industrial-Metaverse will create interactions between the physical and virtual worlds to extend operations in the physical industry. This particularity and the demand for increasing immersion in the Metaverse require using XR technologies called User-Metaverse interfaces (UMI). How such a UMI must be designed for the industrial-Metaverse is unknown. This study adopts a design science approach to design a UMI based on social-cognitive theory (SCT). According to SCT, creating user-generated Metaverse content is crucial to the UMI design. It empowers users to generate content through their efforts, leading to higher self-efficacy and user engagement. We formulate two theoretically based design principles and instantiate a software artifact, which we evaluate in a laboratory experiment with 57 participants. Our study shows the importance of belief in success in the design of future UMI. Furthermore, our design principles show significant positive outcome expectations of users in their interaction with the software artifact.