Audio in on your hifi is the correct place to connect the audio out of a TV. There are more than one kind of audio output and input. You need to match them.
If the TV has a headphone jack or analog RCA audio outputs that would connect to any hifi with an aux or line level analog input.
The most common audio output on TVs is a optical digital audio output. If the hifi doesn't have this kind of input you can get an optical to RCA converter to connect them. Check the TV manual on how to turn on and set up the audio output.