If I install an outdoor OTA antenna, can I just use the DISH Network coax or do I need to run new cable? If I can use it, is there a special way to connect the antenna?
If you can run a dedicated cable, it's probably better to do so. Otherwise you can use a diplexor to share the existing cable run.
You screw it on. You haven't done a search at all for one, have you ?? Give it a try and look at a picture...