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: