Why does my Nikon d7000 flash fEE when I put in my 50mm lens?

I have the older version of the 50mm but because I have a higher end camera it should work. But the shutter release won't go off and it flashes fEE in the info screen. What am I doing wrong? How do I change it so it works?

It depends on how old the lens is. The error means that the camera can't control the lens aperture.

You can still use the lens, but not in auto or program mode.

Here's some info from Nikon

This lens has a mechanical aperture ring to enable it to work with older film cameras. To work with a digital camera, you need to set the aperture ring to f22. Notice that number is orange. That will enable it to electronically know and control the aperture setting.

Set and lock the aperture as above. If the lens is too old, you will have to put the camera into manual mode.