You can either use an HDMI cable, or a VGA cable. You most likely have a VGA cord going into your monitor right now. Newer TV's have a spot for VGA in the back. If your computer has an HDMI slot, then you can use that to hook it up.
Both VGA and HDMI cables can be bought at a store like Staples, Best Buy, Circuit City, etc. (you might even find some at Walmart!)