Superimpose:
1. Open your colored background then the box and make it as big as you want and make sure it's centered. Merge.

2. Open your png and put it wherever you want it in the box then go to mask and click the rectangle masking tool mask out anything that is covering the bottom of the box. Merge and save.

Picsart:
1. Open your colored background then go to draw. Open the box and make it as big as you want make sure it's in the center. Next open a new tab then open your png in that tab. Move it to where you want it in the box. Next click the eraser and then the shape button. Make sure it's on the square and it's on fill not stroke. Then mask out any of the png that's over lapping the bottom of the box apply and save when finished.

Add your text and your done!

Here's the picsart cover:

A/N: lots of tutorials to update today cause I'm gonna be busy all next week XD