Please see the manual for descriptions of the directives.
Note that in this example I have everything in the default locations.
To find the event log files, right click on the logs inside of EventLog and choose properties.
For System, this gave me %SystemRoot%\System32\Winevt\Logs\System.evtx
If this is not working for you, it is possible that the path is incorrect or there is something else going on. In the case of errors, nxlog.log should produce something to go off of, or running the service from command line with nxlog -f after stopping the service sc stop nxlog.