Plug both parts of the adapter - both mini displayport AND usb into your Macbook Pro. Connect the adapter to the HDMI cable, and connect the HDMI cable to your TV. There there should be an "input" or "source" button on your TV remote. Press this button until your MacbookPro's screen shows up on your television.
Presto.
This may simply be an issue with learning how to use HDMI devices on your television.