You can use the model generation mechanism to generate tables from your external database to your warehouse PDM and create the required data source and mappings in your warehouse PDM.
If you are adding the tables to an existing warehouse PDM, the Merge Models dialog will open, allowing you to review the changes that will be made to it before clicking OK to continue with the generation.
The selected tables are generated to the warehouse PDM, along with a data source object and the appropriate mappings.