So it took me ages to try and figure out how to do this but finally I can ok so let's do this.
You can do either white or black shadow- I'm going to do white but I can also explain black.
Unlike superimpose, there's no quick way to do it on picsart, and it can get annoying to have to do this every time but this is the only way I was able to figure out.
Open a png of the person you want shadowed:
Then go to tool » adjust
And turn up the brightness all the way.
If you want a black shadow, you turn down the brightness instead.Then press the tick and click tool » adjust again and turn the brightness up again. Keep doing this until it is completely/almost white.
There are often parts that won't go away but getting rid of them is simple.
You go to the paintbrush tool and select the colour white.
Paint over the parts that won't go away and:
Tadaaaa!
Then open the background of your cover and add the shadow:
Then add the original PNG:
And place them however you want.
Finally, add text and...