Assuming you're talking about a digital camera:Fuji FinePix S1: http://www.dpreview.com/forums/post/2626614
Q: "I am getting a FEE error on a Fuji FinePix S1 Pro Digital, the 300mm lens seems to be connected correctly.?"
A: That information is in the user manual. You need to lock the aperture ring at its smallest aperture (usually f/16 or f/22)
A: Set aperture ring to largest f/number.
If you want to manually select the aperture size using the ring, set camera to M (manual) mode. When you leave manual mode, return aperture to smallest size (largest f/number) again. Some lenses have a lock beside that largest number. Use it then even with the camera in manual mode, you can use the buttons or wheel on the camera to change aperture size.