If your graphics card has DVI you will need a DVI to HDMI converter and an audio cable to make this work. The converter is a small connector that bridges the various connections inside the cable so they match a DVI configuration. Both signals are digital so it’s just a matter of connecting on to the other.
DVI doesn’t carry audio signals, DVI-D does but isn’t standard on many graphics cards. This means you will also need a jack type male-male plug in order to hear anything on your TV. Connect one end from the sound card output on the PC and the other into the audio input on the HDTV.

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Like connecting via HDMI, you may need to modify the screen resolution in order to see the best quality image. Experiment with resolutions until you find one you like and stick with it.
Whatever connection method you use, you may also need to modify your audio settings in order to get the best audio reproduction. Depending on your sound card, you may need to modify the sound output to an external device. This can be done from Control Panel, Hardware and Sound, Sound, Manage Audio Device. Here you can change the output to an external device or HDMI.