If you have any problem to make glossy picture effect, you should follow my this example because I have made it with some easy steps.
Picture: First take a picture to modify.
Selection: Make selection by the polygonal lasso tool (L key).
Inverse: Press Ctrl + Shift + I to inverse.
Now press Ctrl + J and come back to main picture layer and press del key.
Layer settings: Choose Inverse picture layer and reduce "Opacity" as I have done here.
This is the final result.
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