The t_src_item_tmpl, t_src_loc_tmpl, t_src_sales_tmpl are staging tables in Demantra. You need to populate these staging tables with the data in the files that you have downloaded from metalink. Once the data is present in the staging tables, you need to run EP_LOAD_MAIN procedure (or the individual EP_LOADs available for items, location, levels etc. ) that validates the data and moves it to the core Demantra tables. You should then be able to see useful data in the worksheets.
Hope this helps. Good luck!