If you are having difficulty meditating, relaxing your mind or keeping it clear of intrusive thoughts, this is where to start. Concentration meditation can be a meditation in itself or it can be the first step before another meditation practise. Use it to allow your mind to slow down and progressively add time intervals between different thoughts, until you can finally achieve a quiet mind, one that will let you meditate peacefully. This is a skill that is acquired through practise, so there is no point in trying to rush it. Just be patient and practise it daily. A few minutes each day is enough to see improvements.
Concentration meditation consists of focusing on an object or action. Just focus on an object, a single point, a movement, a mantra or a sound. You can start by choosing an object and focusing on it, if your mind strays and thoughts begin to intrude on your attention, bring your mind gently but firmly back to your original focus. Instead of an object you can focus on something else that you prefer. Never pursue a random thought, let them go and refocus, train your mind. Increase the duration as you improve, this way you can meditate for longer periods of time, uninterrupted.