Mapping files should be in the omod/src/main/resources folder. (or if not using maven, in /metadata folder)
There should be a mapping file for each entity that your module/hibernate is maintaining. If you have two objects, then make two classes called FormEntryQueue and FormEntryArchive, then make FormEntryQueue.hbm.xml and FormEntryArchive.hbm.xml and put them both in the resources folder.
The config.xml file has an element called "mappingFiles" that lists off all hbm files that need to be loaded. If using the maven layout, this element is automatically populated with all found *.hbm.xml files. If using the pre-maven layout (ant) then you will need to list off each of your hbm.xml files in that element.