You can manage the BIM data associated to your iTwin by clicking on the Manage button from the BIM data tile located in your iTwin Configuration page.
Once you have clicked on the Manage button, click on the "+ New button".
Enter the name and all relevant information to your BIM.
The Create button is enabled. Click on it.
Once the iModel is created, click on the options menu and select Connections.
For more details on how to create connections, please follow this section: Creating a connection
Once you iModel is created, you can view it in the Model view by clicking on the option menu and select View.