The dSLRs do not support the aperture ring. If you have a lens with an aperture ring, you need to lock it at the largest f- stop number or smallest aperture. The lens also needs to have a control chip in the lens.
The dSLRs use the chip and command dials and not the aperture ring.
If you have an aperture ring without any chips then you need to open the lens iris as large as possible, the smallest f-stop number. Set the exposure time and note the aperture setting displayed by the camera. Now you set the aperture ring to the f-stop number displayed and take your shot.