Running often helps you sleep better. How?
Running and for that matter any physical exercise OR activity promotes good health. And being in good health promotes good sleep. Looking it another way, exercise, running is one of its type, introduces feel good chemicals in the blood. Feeling good means low stress; and low stress means Good sleep.
But you should also make sure to get adequate sleep before going on a good run. Not getting enough rest could result in over-training, that will lead to stress and poor sleep. A balance is required.