The automatic installer puts it at or near the end. I think it can go anywhere really.

Make sure you can both converse with DCS not loaded. Try DCS windowed and small so you can see the TS3 window if people are lighting up and freely alt-tab to check the plugin details. Set all three radios to matching frequencies to reduce the chance you are pressing the wrong transmit key.

It sounds like you've used TARS before and know how it should operate. I haven't had the chance to test it with 1.2.2 so it might simply be not functional.