Create a new file that would have
217x450px,
300 dpi, then take the indicated tool

and create the background for the picture to be.
Fill 0 % on the layers.
Blending Options-Gradient Overlay
Gradient’s parameters:

Take now this instrument

and represent an ellipse of white color.

Copy the new made layer and make use of
Free Transform option to increase the copy and place it the right way, indicated in the picture below.