As Dave8671 said, start by looking at the TV fool report for your location, this is required to determine which channels you can expect to get what kind of antenna you need
- UHF only, VHF-Hi +UHF
- Directional, bidirectional or omni-directional.
Then you can either buy or build an antenna
(assuming your TV has a built-in tuner than can handle OTA signals, it should if it was built in the last 10 years or so but I'm not sure what you meant by 'Nothing at the back of the tv')
If you intend to build one stay away from youtube videos most designs found there are flawed.
One good resource to get started is the digital home OTA forum: https/www.digitalhome.ca/forum/186-antenna-research-development/
Personally I like my m4, there is drawings available on that site : https/m4antenna.eastmasonvilleweather.com/
Other than that gray-hooverman antennas also seem quite popular : http/clients.teksavvy.com/~nickm/
If you want something simple that doesn't require too much material just for a quick test look at the Stealthhawk antenna on the same site as the gray-hooverman, I just mentionned, it's simple to build, personally I was not getting a good enough reception on all the channels I want with it (I can only use antennas indoors which is not ideal....), but it's much simpler to build than the other 2 variants I mentioned so it might be worth a try.
In my case I live 50 miles from most of the channels, which are from New Haven or Harford CT. I would need a 50 + mile ota antenna to even to tune in those channels. A indoor ota antenna I would get hmm 3 channels from New London 2 ion and 1 PBS that is it with a indoor where i live now not a good location due to trees.
Take a pic of the back of your TV I would like to see what you mean.
The easiest antenna by far to make is the simple loop antenna. If you have one channel that's difficult to receive, you can tune it specifically for that channel.
Get a 75ohm coax to 300ohm twinlead adapter, then a piece of solid copper wire such as from Romex.
Look up the frequency of the channel you are trying to optimize for here. Then from:
Wavelength (Lambda) = Wave Velocity (v) / Frequency (f)
or your favorite online frequency to wavelength calculator, determine how long to make the wire. Add a couple inches so you can add loops on the ends.
Bend the wire into a circle by hand, and bend little loops in both ends of the wire with needlenose pliers so it can be screwed into the twinlead terminals.
Or you can use diameter=4537/(6*N+389) where N is the channel number (14-69). As most commercial UHF loop antennas are 7.5" in diameter, you can see they are tuned for channel 36.