Zazen or sitting meditation derives from Zen Buddhism and is the type of meditation Silatha was inspired by.
As much as there are different languages there are many different styles and rituals around meditation. Even within Zen meditation, each monastery and region has their own explanation and realisation of the practice. Thus giving you guidelines following one won't be possible, but we can share some ideas so you can take what you like.
Breath is the central focus. With Zazen meditation remaining in the present tense is the goal. You can keep your eyes open, to stop you daydreaming or getting sleepy. Or close them, so you get less distracted. Mostly the last is used when you start with meditating. When you build a strong practice, you can also open your eyes. Again, it's about finding a way that works for you. When you fell sleepy but get too much distraction with your eyes open, close them, but leave a little opening, so the light comes in.
In Zen practice, beginners practise by facing a blank wall to limit distractions. Direct your focus in a central place about a metre in front of you.
In Zazen meditation posture is crucial. Sit on a zafu (thick round meditation cushion) this will make the pose more comfortable and durable. You can also fold a thick blanket up. The idea is to elevate the hips.
Sit in the lotus or half-lotus. Put one foot on top of the opposite thigh, and the other underneath the opposite thigh.
Draw the knees to the ground, or kneel with a pillow between your legs. When all these seated positions are too painful and this is distracting for you, simply sit on a chair, and keep the head high. Keep your back and neck as straight as possible.
For the hands, place the left on the right, with the palms turned upwards. Get the tips of the thumb to touch to create a slight oval. Your fingers of your left hand, lay on the fingers of your right hand.
Try to find a natural rhythm of breathing. Keep the mouth shut, and breathe calmly through the nose. Let inhalation happen naturally, focusing on extending the exhalation.
Thoughts will come and go but try not to control them. The more you try to stop them, the more power over your mind they will have. As you meditate more often this will become easier. Try to imagine a thought to be a cloud and let it pass by.