Choose a focal point, which can be a spell, a visual point, or even your own breath.
Mantras are words or stages that are repeated in your mind or repeated aloud to help you focus on meditation.
Using a spell or other focus will help you stay on track and prevent your mind from wandering.
You need to practice this meditation method disciplined, because thoughts will come to your mind and you will be tempted to think about other things.
The more you practice, the easier this method will become.