You have never provided any information about your camera, the app you open its images with, the type of file(RAW or jpg). your operating system, or the app you use to edit images.
What did you use to calibrate your monitor? Are you sure your system is actually using the calibrated profile?
If your images appear dark after importing from camera, you didn't shoot them correctly, or your monitor isn't right, or you're looking at a RAW without a color space, or your viewer app doesn't honor profiles.
Let's try to bring a little sanity to this discussion if you actually want help.