CROPPING
Select the Crop tool in the Tools panel.
Drag any edge or corner to adjust the size and shape of the crop border.
Drag inside the crop border to position the image inside the crop border.
Drag outside a corner of the crop border to rotate or straighten.
You can hit the esc key to undo.
Or
In the options bar, select w*h*resolution, and enter your desired size,
for example, enter 1920 px, 1080 px, or 5 in, 7 in
Make sure to specify px or in in your entries!
Press Return to complete the crop.
TONAL ADJUSTMENTS IN PHOTOSHOP
THE HISTOGRAM
Window > Histogram
A histogram illustrates how pixels in an image are distributed by graphing the number of pixels at each color intensity level.
The histogram shows detail in the shadows (shown in the left part of the histogram), mid-tones (shown in the middle), and highlights (shown in the right part).
A histogram can help you determine whether an image has enough detail to make a good correction.
ADJUSTMENT LAYERS
Adjustment layers give you additional editing flexibility. They allow you to re-edit image adjustments you’ve made, and protect your original image from direct changes.
Let's experiment with the LEVELS adjustment layer and the CURVES adjustment layer.