To perform this you will have to map the class of the work object to your custom table that you have created.
Configure/Designer Studio > Data Model > Classes & Properties > Database class Mapping
Use the New External Database Table Class Mapping button (for externally mapped classes only) to create a new database table instance or edit an existing database table instance and properties that associate a class (and its derived classes) with an existing relational database table or view in the Pega database or an external database.
Another option is:
-- Go to Records > SysAdmin > Database Table
-- Select the class which you want to map to a different table.