The antenna should have two screws, to which the old flat twin-lead would have been connected. Get an outdoor rated matching transformer like this:
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=180-010
Use a compression F connector to terminate the coax and coat the threads with silicone grease before making the connection. Make a 12" loop with the coax and use a nylon wire tie to secure it to the antenna in a position that won't allow water to enter the connector or drip down to the balun.
Coat all connections with silicone grease after cleaning the connecting points on the antenna because they have rusted over the years and install the transformer. You should be able to get these at any hardware or big box store. DO NOT use the crimp-style F connectors, use the compression type.
How far from the TV is the antenna located?
Connect the antenna directly to the TV first. If you don't get much, replace the antenna.
Make sure the TV doesn't have a TV/Cable switch, set to Cable. If it's set that way, UHF won't come in.