Google a soybean equilibrium moisture chart.  Run the fans when the chart says the air is making the moisture of beans that you want.  The warmer the air, the quicker it will happen.  When you are done, make sure you run the fan for a few hours on a dry day to keep the bottom ones from sticking to the floor.  People on here are always worried about this, but it's simple to do, and makes a lot of money.  I have added 3-4 points back to my beans just by pushing a button on a bin fan.  This year we got them wet enough that I won't have to do it.