Upload & Sell: Off
You're probably in M mode, where exposure compensation is not available. You can adjust exposure compensation with auto ISO in Av, Tv, and P modes. If you use Av or P mode you can also set a minimum shutter speed in addition to exposure compensation while using auto ISO.
Example: Av mode, auto ISO, +2/3 exp comp, 1/250th minimum shutter.
(This will raise ISO to 25,600 before it lowers the shutter speed below 1/250th.)