Audio is a doddle. By a cable - it will have a headphone jack on one end (ie identical to what you would see on the end of a pair of headphones) and the other end will be two connectors, a white one and a red one (explained above). You can easily pick up a cable of 10 meters for around $30 in one of the computer stores. Longer or shorter if you need it.
The headphone socket end of the cable goes into the headphone socket on your PC (note, this will stop your PC speakers working as it is the same as plugging in headphones). The red and white ends plug into your TV, or, for better sound, your home cinema system.
Don't forget, when you plug these cables into your TV and / or home cinema, you will need to change the Input setting on your TV to be able to watch the signal. There will be a button on the tv and / or remote which allows you to cycle through the TV inputs (ie AV1, AV2, S-video, RF etc).
If you do have an s-video output on your PC you might need to change your PC settings to get it to output the correct signal (ie clone) to that port.
Ask here and I am sure you will be directed in the right direction. Once it is all set up it is easy.
Secondly, you might find, as I did, that you have multiple bits and pieces (ie Now TV, Playstation or Xbox, PC etc) trying to plug into the same places on your TV or Home Cinema. You can solve this by buying a switch box - all the cables plug into it and you select to watch the TV, the Playstation, the Xbox, the DVD, Now TV or whatever. They cost next to nothing, say $50, to support 4 items.
You have to manually select what you want to watch. I have been looking out for switch boxes that use a remote control but haven't come across them yet. Does anyone know if you can buy them?