Typically, the baseCS is the first node type to be placed in a model.

Selecting (Create baseCS ) opens the Create baseCS dialog. Here you can select a model in your DGN to place the baseCS in. Existing models are displayed as well as an option to create a model and place the baseCS at its origin simultaneously.

When the baseCS is created, it appears in the View Window, and its node appears in the Graph. The baseCS node's technique is AtModelOrigin which has one required input: DGNModelName. The inputted value for DGNModelName is the model you selected in the Create baseCS dialog.