Start by creating a new document.

Fill the background with black colour.  Set the foreground colour to white.

Select gradient tool with the settings shown at the top bar.

Apply it several times to create an interesting effect.

Keep going ....

From "Filter" menu select "Distort>>Ocean Ripple ". Apply settings as shown. ie Ripple Size of 1 and Magnitude of 3

From "Filter" menu select "Brush Strokes>>Accented Edges". Apply settings as shown. ie Edge Width is 1, Brightness is 44 and Smoothness is 5

And the result:

Now save your work.