unfortunately that is one of the cheap HTIB (home theater in a box) style units. often the cheaper ones are very limited with external inputs (they only work well with the included dvd player). for that unit you are limited to only RCA (red+white) stereo 2.0 audio input from external sources.
you will want to list your tv model number and if its a separate box than the htib that you bought for blueray you may want to list it. or, at minimum what outputs they have.
also, what device are you trying to get sound from that you are having issues with? (for instance you want to get sound from the tv using netflix but its not working or the dvd player in the htib broke so you want to connect a new one up for audio and its not working).
please do be aware that you will not get surround sound from external sources regardless. the best you will get is a faked version if your htib supports pro-logic but its not the same.
your manual
http/www.manualslib.com/products/Panasonic-Saht740-Home-Theater-Receiver-19242.html
its rather basic and not very revealing.