Tutorial:
Create document 640×480 pixels.
Fill it with white color. Create a new layer name it “circle1″. Select Brush Tool (B). Make a circle similar to mine:
Master Diametar: 300px
Hardness: 100%
1. Make a light blue circle with eclipse tool (hold SHIFT button to make a circle).
2. Duplicate the circle – CTRL+J. Make it a bit smaller using transform tool – CTRL+T. Fill it with a darker blue gradient.