No sound from external speakers system

most set have jacks marked "audio out" which could be RCA type jacks, or a coaxial or optical output . Connect a cable or cables from whichever one of those is compatible with the inputs on the back of your stereo receiver.

Check the audio settings and make sure that you did not set it to external speakers only.

Hooked up wrong or maybe they are just for your dish or cable and not hooked up for your game system

Input 1 is an INPUT so you can't connect external speakers there and get sound from the television, which is what you are attempting.

Your two choices are the 3.5mm minijack hole that says AUDIO OUT terminal, which is under the Ethernet Terminal and the DIGITAL AUDIO OUTPUT terminal, which is under Input 7. If your external speaker system does not have a 3.5 mm minijack input to accept the 3.5 mm minijack cable then this isn't going to work. There are cables where one end is a 3.5 mm minijack and the other end is an RCA so you can try that and it MIGHT work. Other than that the Sharp televisions are known for not carrying sound over the fiber optic cables consistently so even if you bought a fiber optic cable and connected it between the digital audio output and a speaker system or sound bar there is no 100% guarantee it'll work. It is worth a try anyways.

Ok, I need more verifications:
1) Your TV is Fujitsu Siemens PlasmaVision P42VHA40 Monitor which does not have tuner? If not, please provide the make and model of the TV.

2) What kind of cables you are using to hook between the cable box and the TV? HDMI? Component video (Red, Blue, and Green cables withe RCA plugs)? Composite video cable with Yellow RCA plugs?

3) Are you trying to get the sound to come out off the TV speakers or through the stereo system?

Try switching the external/internal speaker switch on the back of the tv to internal. This way you should at least get sound (from the TV not the sound system) when you change the volume of the TV itself.
Explain your set up if you need more help. By that I mean what do you have hooked to the TV and sound system, Satellite or digital cable box DVD ?
Make a note of where all the inputs to the sound system come from.

The monitor must plug into the PC as the external speakers did.

I had what may have been a similar problem and even talked to Westinghouse to see what I was doing wrong. Woman suggested there was a problem with the audio output port and suggested I exchange tv for another one. When the new one had the same problem, I discovered that to get audio out requires the volume to be turned way up on the tv (set speaker preference to external only if you don't want sound from tv speakers as well). If you have a digital optical connection on both the tv and the home theater, the sound output is independent from the tv setting and is easier to work with.