You can't get night ringing over the paging unless your amplifier has that circuitry built in, or you add an external "black box" that uses a station's ringer to generate a tone that can be broadcast over the speakers.
Some of the Bogen amplifiers that Avaya sells have a couple of terminals that you connect the tip and ring of a station to, and the 90vac ringing makes a warble tone come over the speakers.
Valcom, Viking Electronics, and others make interfaces that will do the same thing with other makes of amplifiers.
As far as the hookup/programming, use a spare station port, give it the lines that you want to ring in the night mode, set them to NO ring, put the station in the night service group via #504, and assign a night service button to Ext. 10 via #503