Another tutorial on request on how to make gradient shadows to transparent, your final result will look like the image below:
1. Open your canvas and select the gradient tool. Use a fill from black to white
2. Draw the shadow from left to right, which gives you a black-white canvas.
3. Layer - Add Layer Mask - Reveal All
4. Choose a gradient with these settings black-white-black:
5. Drag from top to bottom
6. Voila! Now move your shape or image over this layer, and position it so that the shadow suits your needs. It can be as big and black as you want.