i think you need to ensure that you add a namespace and reference to the object's Code Options
Then you can use the objects from the DLL within code stages:
Application app = new Application(){ Visible = true }; Workbook wb = app.Workbooks.Add(); Worksheet ws = (Worksheet)wb.Worksheets.Add(); ws.Visible = XlSheetVisibility.xlSheetVisible;
As you can see, you can also use the named enums, but just like in C# you need to specify it fully (XlSheetVisibility.xlSheetVisible instead of just xlSheetVisible)
hope it helped