mr.crane
That what you bought is not a tv it is a moniter, By federal law in the USA any set cannot even use the term tv or television in an advertisement at a store if it didn't have a ntsc or now atsc tuner in it. If a store sold you it and the advertisement called it a tv or television I would be takeing it back to that store for a refund or exchange. Now if the store plainly calls it a monitor they might get by with something like tv monitor but thats just a guess,They are still skirting the law.
Now as for your question about hooking an antenna to it. Only way I see is buying a box with an atsc tuner built in it like the older switchover boxes when they went from ntsc to atsc or a box with an atsc tuner built in it that also has an antenna connection. There are boxes out there.Oh and another way would be,(hint better than any box) is if got an old laptop with a hdml connection,Add a usb atsc tuner dongle to plug into it(they not to much at amazon and ebay) but can stream the antenna to the laptop then to the tv through the hdmi cable. And can also turn that laptop into a over the air antenna dvr,But also can if use something like Webgrab++ and do your own tvguide to connect all channels together and will be just like cable. Or you can buy an dish airtv.