Well ... I have PSE 11, but this is what I do. Duplicate, color the duplicate with a dark grey & add Gaussian blur, about 10-20 pixels, depending on how big the element is. You have to try and see what you prefer. Then I move the shadow behind the element, nudge it a bit up & right (or whatever angle I want the shadow I want).
If it's a photo, I use Filter - Distort - Liquify, and pull the top & bottom side a bit down. Twist & turn til I'm happy.
If it's an item or a person, I add a new layer on top of it. Uses the brush, and the same dark grey, and paint a line at the bottom of the layer I want shadowed. Add the Gaussian blur again, and move the layer to the back. This gives a darker shadow, just where the item meets the ground.
Play with blending modes (I like Multiply for shadows) and you probably need to lower the opacity to get a good look as well.
Here you can see the extra added shadow layer under the elephant's and giraffe's "feet" (probably called something else in English, but I'm too lazy to look that up) and under the watermelon.
Also, at times, when I do this for a person - I use Image - Transform - Skew (or Distort) to play with the shadow. Like I've done with John's shadow here: