In order to watch a TV signal you need a device with a tuner, which TVs have built-in. The Optoma does not appear to have a tuner. I don't have much experience with projectors, but I would guess this is not a common feature. Are you looking to connect to your antenna with a coax cable, or something else?
I use a HDTV tuner in my set up. You will need an ATSC tuner like a Channel Master CM-7001, not enough posts to use a link. You can search other places and find some good deals. You will also need something to amplify the sound, receiver or the like.
If your computer or laptop is connected to your projector , check out these products...
This Silicon Dust dual tuner ($65) accepts your TV antennae and sends it to your PC or Laptop over ethernet to Windows Media Center and your Projector is connected to your PC or Laptop as a primary (or secondary) display ..... Other more sophisticated brands are available to replace Set Top DVR's using a cable card