Create a Radial gradient, from bark to light blue. Use the settings here, then drag from the middle
of the circle.
Step: 3
Create a new layer and change the gradient setting to Linear, Foreground to transparent and change your forecround color to white.
Step:4
Drag the gradient tool from the top to the bottom, with the top white.
Step:5
apply the the Edit > free transform tool
Bring the bottom to almost 1/2 way. Bring the top and sides in a little bit until it looks similar to the picture
Step:6
To make more realism add a slight gaussian blur to the highlight and rduce the opacity a little
