Rinse them with water - How to Make Peanuts Tutorial

Place the large colander full of peanuts into a sink and thoroughly rinse with running water. You’ll need to remove any excess dirt or debris that you loosened from the peanut shells while you were scrubbing them. Continue rinsing the peanuts while gently stirring them around the colander until the water runs clear.
If you are working outside or with a large batch of peanuts that won’t fit in your sink, you can also rinse the peanuts outside with a water hose. Keep in mind that it will be more effective to rinse your peanuts while they are in a container with holes that allow the dirty water to easily pass through.