Choose the
Ellipse Tool (U) again to draw on the button’s central part a kind of illumination coming from beneath, colored in black.
The layer’s parameters:
Blending Options>Outer Glow
Blending Options>Inner Glow
Blending Options>Stroke
Make a copy of the recently made layer and select the
Free Transform option to make the copy smaller, applying different parameters too.
The flare’s placement should be changed with the
Move Tool (V) when having opened the next shown palette:
Blending Options>Gradient Overlay
Gradient’s parameters: 
