I have the aperture at the lowest number but when I look into the viewfinder everything is dark and when I turn the aperture to lighten up the viewfinder it gives the fee
It sounds like the mechanical lever in your camera that normally couples the aperture to the camera to lock it to the widest opening for focusing is locked into the fully closed position, or that the electronics are not allowing the lens to open to fully open, depending on the type of lense being used.
Also, it could be an issue with the lense.
The simple way to test this will be to remove the lense, and to rotate the aperture ring while looking through the lense. If you see the aperture getting larger/smaller the lense aperture is fine. If it is not - the lense is damaged and needs to be replaced, or at best serviced. This can be done through Nikon, a local shop if you have one, or through online shops, I'd recommend KEH Camera in Atlanta if you have to go that way.
To test the camera side, if the lense appears to be working is also simple for the mechanical lever. With the lense removed, hold the camera in front of you looking into the lense mount. On the left side, you should see a small lever like piece. With your finger, see if this piece will move downward - it is spring loaded and should smoothly go down and pop back up. If it doesn't go down, or doesn't spring right back up, then the issue is on the camera mechanical side.
If both of those check fine, you may try a manual focus Nikon mount lense if you have access to one - to eliminate the camera electronics from being an issue, and the lense from being an issue as if this lense doesn't work, it's a mechanical issue. If you have access to another AF lense you know is working, and it doesn't work on your camera, you've narrowed it down to either the mechanical lever, or the electronics.
Most likely culprit is the lense itself.