So you have an iTwin subscription and need to make an iModel.

Firstly you might want to ensure you have a project registered, if not, go to https://itwin.bentley.com/.

Click on Register a Project. Follow the instructions paying particular note of the Data Center.

After you have created a CONNECTED Project it will have no iModels, it is empty. Some consideration should now be made into how you want to connect to this project. Where does you data reside?

If your data is in a CDE like ProjectWise it would be wise to associate the datasource to the CONNECTED Project.

iModels can be created from the ProjectWise Share that is part of the CONNECTED Project.

Click on the Create an iModel button.

A name and description is all that is really necessary at this stage, the location will determined by the data you connect to. For more detail on creating iModels go here.

Click on the context menu in the lower right corner.

Click on Connections and then the Create connection button.

It is at this point where you select either iTwin File Service or ProjectWise for your source data.

For details on container files, federation and general best practices go here.

For more detailed information on synchronization go to the Synchronization Wiki.