Start slow, don't remove all the tack at once and expect your horse to know what to do
Firstly, gain trust with your horse. That could be anything from groomin sessions to join up. I have two horses that will actually follow me around in the pasture freely with nothing making them move forward (halter and lead rope). Once you've gained their trust, it will be a lot easier to teach them liberty and they won't run away!
Hope this helps!!