Create a new document with a transparent
background layer. I like to work with lots of space,
so I've gone for a 600x600 pixel canvas. Use the
Elliptical Marquee Tool make a decently-sized
circular selection, holding down the SHIFT key as
you drag it out so that it keeps equal proportions.
Edit > Fill this circle with a solid black color. Without
losing your selection, run Edit > Copy and Edit >
Paste to duplicate this circle and move it a little to
the left so that the two circles are overlapping a little