The tnsnames.ora file is not used by this connector. However finding it and looking at it is necessary to do if you have a local installation of Oracle on your computer.
The service name to use if you have an Oracle XE installed is XE as default.
Oracle is often installed as a directory under root called something with ORACLExxxxx
The path to the tnsnames.ora for my installation of Oracle XE is
If your path is different you could search for tnsnames.ora on your harddisk....