How do I turn on wifi on my tv

You read the manual that came with your TV.

If it does not have wifi then you cant put wifi on your TV.
If it has an ethernet port and no wifi then you can get a wireless bridge to receive wifi and provide etherent to the TV
If it has neither then it has no "smart" functions so even if you could hook it up to wifi/internet it would not provide a single extra function/feature.