How does DSM work with existing design libraries? Is there a conversion process?

Brand.ai customers can contact support to migrate a Brand.ai library to their DSM account. Note that Brand.ai artboards are not supported in DSM. 
Craft Library users can import a library directly from the DSM plugin; just select the libraries you’d like to import, and they’ll be available in DSM. Please note that Craft Library groups are not supported. 
Sketch Library users can easily upload assets from a Sketch library to DSM by selecting the items to upload in the Sketch document, then clicking add in the plugin to upload the items to DSM.