If you google "how to meditate" or "beginning meditation" or "mindfulness meditation" you will find many guides to how to begin.
Typically, they will instruct you to focus on your breath, and to try to think of nothing. At first, all kinds of intrusive thoughts and feelings will come in. Your nose will itch, you will think about what to have for dinner. The instructions say to gently return your focus to your breath.
It can be helpful to set a timer for 10 minutes or so in the beginning. That way you aren't thinking about the time.
It takes lots and lots of practice--lol, that's why they talk about PRACTICING meditation.
There are other kinds of meditation, too, but this is probably the most widely recommended way to start.