The most basic thing that you must know before you can remove bed rails from the Ford Ranger is whether the rails are attached to the top or bottom of the Ranger. Some bed rails are held to the truck bed with bolts installed in the truck bed from above with trim covers hiding the bolts whereas other bed rails are anchored from underneath the truck bed.
If the bed rails on your Ranger are held in place with bolts installed in the truck bed from above, the first thing you need to do is to get remove the trim covering hiding the bolts. Use a pocket screwdriver for this purpose. After you have removed the trim covering, you will see the bolts that are holding the rails attached to the truck bed. Remove these bolts with a socket set. There may be more than one bolt holding the rail in place. Remove all the bolts simply lift the rail and take it away from the Ranger.
If the bed rails on your Ranger are anchored from underneath the truck bed, removing them will be a little more difficult. Climb into the truck bed and lie down with you face towards the sky. Position yourself beneath the lip of the bed wall so that you can see the fasteners. Analyse the work space that you have at your disposal in order to choose the appropriate tool for removing the fasteners. Use either a socket set or box wrenches depending on the available work space and remove all the fasteners. Get up from the truck bed and lift off the rail from the truck bed.