I have no sound from pc to tv using Jack-to-RCA

Hey guys.. I've been trying to get this fixed all dayy.. Recently i connected my desktop to my lcd lg tv, using my vga cable. Image is perfecttt, but as It has no sound, i bought a Jack-to-RCA cable or whatever.. I plug it in and so on, but i cant hear anythingg.. when i plug the jack into the pc, a popup comes up from realtek HD audio manager asking me if it's a line in, mic in, headphones, front speaker out, rear speaker out, center/subwoofer speaker out, and side speaker out. I have tried with headphone and line in.. I'm guessing it's line it, but oh well I have tried it all and it still doesnt work. I plug in my regular headphones and nothing has to be done as it works automatically. I honestly don't know what else to do.. Thanks in advance.