That Ryobi locks the spindle with the button / lever that is on top of the motor housing.
Once it's locked, either get the wrench that came with it, or any 9/16" wrench you have laying around. With the bit up, insert the wrench into the open window on the side of the router, put the wrench on the black hex nut just below the bit, and turn counterclockwise to loosen the chuck. Then just pull the bit out.