how to retrieve fault codes from obd-2 emission. on 2007 Ford Explorer Sport Trac

today engine emission light came on.engine started to miss at idle as well as while driving.

Go to your local parts store or call them first. They will usually read check engine codes for no charge. The description you gave sounds like you have a misfire condition usually caused by bad spark plugs or coil failure.
Thank you very much for your response! I aprreciate your help.