How do I connect my desktop pc to my HDMI samsung tv along with an external subwoofer?

Well, you are talking about two separate sound outputs. The audio built into the PC and the audio system that is built into the HDMI system. If you don't use the audio from your pc...the sound is heard from your hdmi device...in this case the TV. Most TVs don't have a spot to simply attach a subwoofer and you have to once again send the output (from the TV) to an external amp...where you can attach external speakers and a subwoofer. Or...you can simple use the PC audio to plug into a speaker system with a subwoofer. Your TV becomes strictly a MONTIOR.