You do it over the lens as there is no electronic communication between camera body and lens.
Then for metering you need to use either AV, so that camera will chose a correct speed for the given F stop, you set on the lens. To make more easy for camera, keep your ISO also on AUTO.
Or you may use Manual "M" for full manual setting of all parameters including Shutter speed, ISO and of course aperture as you have done before.
Pay attention to your focusing. You can get assistant via LiveView if your camera body has it or you can use Magnified view during focusing and in my personal experience, 10x does a great job for perfect focusing.
Post more with any problems on the way as you can run into something new when camera not fully on auto.