By buying a converter box. Click on the link above.
If so, how does it free up the airways?
Digital signals take up far less bandwidth than analog signals. So they can give a TV station a digital channel (which can be broken up into several subchannels)in exchange for the analog channel, and end up with extra spectrum to re-sell. The broadcaster ends up with up to 5 channels instead of 1, and the consumer gets the short end of the deal.
Thanks.
And I also noticed the gov will be selling the newly freed airwaves to the wireless phone companies.
Yes and no. Full-bitrate HDTV signals transmitted digitally using the ATSC standard take up the same bandwith as do standard-def analog signals. That was an explicit design goal. Stations that don't put out hi-def programming, however, can do exactly as you state: cram multiple standard-def "sub channels" into the same bandwidth. Some stations do a combination of both: They transmit one HD sub-channel whose bitrate is limited (lessening the image quality,) and one or more additional standard-def sub-channels. This is commonly done by PBS stations.