First, be sure you actually need a converter. If your TV was built after 2007, the FCC mandated that it have a tuner capable of OTA digital (ATSC/8VSB) reception. Check the spec's, an online search for the manual based on your model number will usually answer the question. Virtually all TV's with digital capable tuners default to cable mode, so you'll need to use the setup menu on your TV to change the tuner to 'air' or 'antenna' mode. Cable and OTA use different digital formats.
If you opt for a converter, consider the HD capable units referenced in this thread:
http://forum.tvfool.com/showthread.php?t=2882
Unless you are willing to go to extraordinary measures, the signals to the north are too weak.