There are many ways to start on a path of meditation and Goenka's described path & interpretation of the Buddha is just one. If you want to see serious benefits from Goenka's path, I highly recommend that you attend one of the 10 day meditation courses that are available worldwide.
Until then, I will give you some additional context to Goenka's meditation instructions to help with what you are currently working on.
Observing bodily sensations with equanimity (non-reacting) is a very important aspect to the meditation, but it should not be started on right away. The first four days of Goenka's meditaiton course is focused on Anapana meditaiton, meditation of breathing. This is done to sharpen the mind, allowing you to feel the subtlety of feelings, and allow it to stay with a directed object for consistent and long periods of time.
You mention that you are not able to see how you are reacting to your bodily sensations and this is likely why. Observing bodily sensations will not produce much benefit until some amount of concentration has been practiced. Once your mind can feel in a more subtle manner and also stay on a sensation for longer periods of time, you can begin to see how also on a subtle level, the sensations either feel pleasant, unpleasant or neutral and that along with those categories of feelings, your mind is craving for the pleasant ones and creating aversion for the unpleasant/neutral ones (aversion to neutral feelings is often the feeling of boredom). And then once you see those reactions taking place, you can simply observe those reactions and over time those reactions reduce and become calmer and calmer.
That's the general idea behind it, gaining concentration, and then using that concentration to observe your feelings, see its parts, feeling & reaction and work to reduce the reactive part of your mind.
But to start, I would spend a fair amount of time practicing breath meditation. To do that, you simply need to observe your breath coming in and going out, without trying to control it. Breathe naturally. Observe for as long as you can and eventually your mind will wander to something else. Once you realize your mind has wandered away, smilingly bring it back again and start again observing the breath. By repeatedly doing this, you are building concentration and reducing the habit of mind wandering. It is very important not to get frustrated when your mind wanders (or even to get frustrated if you get frustrated!) but instead accept that this is the current nature of your mind and to just gently keep guiding it back to the breath.
Over time, the duration of continuous time spent noticing the in & out breath will increase and the duration and frequency of mind wandering will decrease. Once you get to a point where you can keep your attention on your breath for at least 1 minute continuously, that is probably a good time to start trying to observe your bodily sensations.
You can incorporate this naturally as you practice Anapana by feeling the breath coming in and out at the entrance of your nostrils and below it. Knowing the breath coming in and going out and also feeling the sensations of the breath passing over that area as the breath comes in and out. As your concentration grows, you can reduce the space focused on your upper lip and entrance of your nostrils to a smaller and smaller area to help increase the subtlety of your mind.
When you can sufficiently feel sensations in that area when you are breathing in & out, you can begin to observe sensations on other parts of the body. Trying to still keep a small area of attention, you can move your attention up and down your body, part by part, feeling the sensations briefly, and then moving on. If you don't feel anything right away, or it feels foggy, you can stay there for a minute or so and you might start feeling those sensations, otherwise keep moving. The order that you go in does not matter, but it is important that you don't linger on areas for too long and that you cover every little tiny part of the body. Goenka suggests going head to toes to toes to head, part by part and repeat.
After you can subtly feel the entire outside of the body, you are free to try to pierce your attention inwards to feel the inside of the body, going part by part.
If at any point your mind becomes too agitated and difficult to practice observing bodily sensations, then its good to come back to the breath meditation until your mind becomes calm and stable again.
There is more to the practice after this point, but I don't want to overload you at the moment. Also please keep in mind that I've described a progression of practice and it is not good to try and jump ahead when you have not sufficiently practiced prerequisites.