This data is stored in the PRoduct Information database (ProdInfo for short) that the Fabrication Products use.

Use the Product Information Editor application to edit/add data.

A few things to note: 

- By Default, the Revit Fabrication Configuration does NOT have and Product Information setup last I looked. 

- Once you load the config, and content that references the ProdInfo is cached in Revit and will NOT be updated if it's later changed in the ProdInfo database even when reloading the configuration.