Many electric pumps have an option for both inflation and deflation, where deflation essentially does the reverse of pumping air into your mattress (sucking out all air so that it's fully deflated). To inflate with an electric pump, simply insert the valve, plug in the pump and wait until your air bed reaches the right level of firmness for your needs. If yours doesn't have the automatic deflation feature, it's usually very simple to do without a pump. You can either let the mattress air out naturally by simply opening the valve, or press down and spread out the mattress to remove all air manually.