The DevForce Developers Guide, installed with DevForce Classic, has information on how to get started. See the Chapter 2 topic "Map a Business Object" for how to point to your database. Chapter 4 on "Business Object Mapping" also has additional details.
I would first review the documentation and then give the Object Mapper a try with your database. If you then find that you need to tweak something we have several different customization points, including the AdoProviderHelper, DataSourceMappingInterceptor and IAdaptorProvider. The help reference has more information on these, but I'd wait until you know you must customize before you dig into these advanced topics.