How do you use hdmi with msi's n9800gt

You can use an adapter such as this http://www.newegg.com/Product/Product.aspx?Item=9SIA67038S8758&cm_re=hdmi_dvi-_-9SIA67038S8758-_-Product
or a straight out cable such as this http://www.newegg.com/Product/Product.aspx?Item=N82E16882422117&cm_re=hdmi_dvi-_-82-422-117-_-Product

In order to also transmit audio, you will need to connect your motherboard(or soundcard if you have one) to the video card with a 2-pin cable that came with the graphics card like this http://www.newegg.com/Product/Product.aspx?Item=9SIA2970S36973&cm_re=spdif_audio-_-9SIA2970S36973-_-Product