Click the first keyframe in the Timeline, draw another circle by using the same method mentioned in Step 2.
In the Transform tool, set its size as 188*188, and the position in the center of the Canvas (150,70). Note: The position of both circles should be the same, which is a key factor to create such effect.
In the Shape panel, choose Radical as the Fill Style. Set the colors of the Gradient pointers as indicated in the picture below.
Set the color of the first pointer as R:102 G: 204 B:255 A: 0%.
Set the color of the second pointer as R:255 G:255 B:255 A: 100%.