Step 1 :  Create the duplicate Layer by clicking Ctrl+J
Step 2 : Click on "Magic Wand Tool" from right pane and select the image, that will show as given below



Step 3 : Click Select > Inverse or Shift+Ctrl+I for selecting the images, then we have to select the rest of image with using Quick Selection Tool, it will looks as below image




Step 4: Copy the Selected Image and Paste it to the New layer or else we can do it Layer via copy and name as girl image.



Step 5 : Copy the Same Layer as duplicate by clicking Ctrl+J and name as shadow image

Step 6: Create New blank Layer by Clicking Ctrl+Shift+n and named as Background and fill with white color by clicking Shift +g (Paint Bucket tool)


Step 7 : Select the Shadow Image layer and click Shift+f5 to fill the image with Black color as shown below


Step 8 : Select the Shadow Image layer and select Edit > Transform > Distort or By clicking Ctrl+t



Step 9 :  Change the position of the shadow image as its looks good as shadow of its own image (hold Ctrl key for better transform)

Step 10 : Now Select the Filter>Blur>Gaussian Blur 

Step 11 : It will prompt to you the below window to modify the shadow according to your requirement and click OK.

Step 12 : Now the Image is having good shadow....COOL !!!!!