So the first take home first thing you can do, this is called your chin tuck. As you gently guide your chin back in space, the top back of the head rises up towards the ceiling. Hold for a couple of breaths and then release. Do this three or four times and this will help to re align your neck muscles strengthening the ones that need to be strengthened in the back and relaxing the muscles in the front. do this a couple of times a day to start off. You can also practice the chin tuck up against the wall.
This may be easier for you to feel the sliding action and feel the back of the head actually sliding straight up aligning the screen over the shoulders, over the hips, over the knees and over the ankles. Stand up against the wall. So you can feel your seat your hips, your shoulder blades in the back of your head against the wall. Place your two fingers on your chin again. And gently slowly slide the back top of the head of the wall as you tuck your chin in. Hold each or two to three counts or two or three breaths and then release