Photoshop effect

[aggelosmour]

Hi! Can anyone remind me how can i add an effect like this in this picture. It is like a small shadow but not exactly a shadow effect. You can increase it or you can turn it on the left side.  

[S_Gans]

Hope this video helps - see attachment.

NOTE: when recording this, I errored on being able to actually REACH INTO the image when the dialog box is open, to reposition the shadow. You CAN do that, but I could not demonstrate it here...