yes , do you have the operators manual? it explains how to do this there.
is this a new or used vehicle? do you have the factory nissan remote and IR headsets?
if so, the remote is used in back for each screen separately. there is a "1" and "2" to denote which screen the remote will work with at any given time.
the IR headsets, if nisssan factory, have a 1/2 selection on them. headset switched to #1 should be used on the driver side and #2 on passenger side.
up front, the driver can listen to a separate source from the rear and if you have a external device plugged into the RCA ports (or a DVD OR a USB drive), each screen (up front plus each rear) can have a separate source going to it all at the same time.
again this is in the operators manual to get more details on...