Use the Auto button to change the histogram significantly. This expands the dynamic range of the image, brightens lighter areas of the image and ensures there is a black point.
The sliders in this area (Exposure, Contrast, Highlights, Shadows, Whites, Blacks) will help fine-tune corrections. Change the values by moving the sliders to the left or right. These sliders are non-destructive, so any changes you make can be refined later.