assuming windows 7, click start>devices and printers. now right click the bluetooth adapter and select bluetooth settings. under discovery, set it to allow device to find your computer. make sure the bottom option to show icon in notification area is on as well. now right click on the notification icon and select receive file. a box should popup saying waiting.... now use your phone to find your computer name and send it.
if you don't have any bluetooth adapter showing, you'll probably need drivers. check your mobo support download pages.