It’s impossible to think about not thinking. All we can do is become fully present, which takes practice. When we are thinking, we are not present, but rather we are in our head. So we simply have to practice being fully aware with non judgemental curiosity about our surroundings and even our bodies.
There is so much around us and within us at all times that we tune out. We have to tune back in order to find peace and freedom from our own mind. Thoughts will still pop up, but if we are aware of them too, even then there will be peace.