You aren't being clear: is there a problem with exposure, sharpness or both?
And, what focal length are you shooting in?
Getting the exposure brighter will require either a slower shutter speed, a wider aperture, or a higher ISO. Which of these you use depends on the scene you are trying to capture and on your technique as well as the focal length you are using. If you are shooting handheld with a 400mm lens, then you typically don't want to slow down your shutter speed. With the settings you describe, you would most likely brighten the scene by raising your ISO. But sharpness is something different -- your images can be soft because camera movement can show up with a slow shutter speed or you could have focus issues.
It all just takes practice over a learning curve.