To convert a design file into an i-model, you need the Bentley DgnDb i-model Importer. Different Bentley applications support different versions of i-models. For example, Bentley Navigator CONNECT Edition versions up to Update 2 support i-model version 1.5, whereas, Bentley Navigator CONNECT Edition Update 3 and later support i-model version 1.6 and later. To create an i-model of a version, you need a matching version of i-model Importer installed. In this update, MicroStation allows you to select the version in which you want to publish the i-model. In the Publish i-model(s) dialog, a drop-down is added to select the i-model version.
To know more about i-models, refer to the help topic Advantages of the i-model.