Set an intention and pick your crystal accordingly to its properties. Place yourself in a comfortable position sitting up right or laying down with a straight back. Hold the crystal in your left hand and place the palm of your right hand outwards. You may also place the crystal on your body or have it laying nearby during meditation. Visualize your intentions let all energy and thought flow for 5 -10 minutes. Focus on your breathing.
If you prefer a guided meditation you can always look for a fitting video on YouTube for guided meditation or to follow an pranayama (breathwork exercise).