You start by sitting with your eyes partially closed and turn your attention to your breathing. Breathe naturally, preferably through the nostrils, without trying and thinking of controlling the breath. And you should try to become aware of the sensation of the breath as it enters and leaves the nostrils. This sensation is your object of meditation. So you should try to concentrate on it to the exclusion of everything else.
At first, the mind will be very busy, and you might even feel that the meditation is making our mind even busier. But in reality you are just becoming more aware of how busy your mind actually is. There will be also a great temptation to follow the different thoughts as they arise. But you should resist this and remain focused only on the sensation of the breath.
If you discover that your mind has wandered and is following your thoughts, you should immediately return it to the breath. Repeat this as many times as necessary until the mind settles on the breath. If you practise patiently in this way, gradually your distracting thoughts will subside and you will experience a sense of inner peace and relaxation.