Create a fresh document size of 500 x 500px resolutions 72dpi then select the Paint Bucket fill up the canvas with Black Color, now select the Rounded Rectangular Tool and draw a shape with any color as demonstrated below the go to Layer => Layer Style and set the following Style.
*Gradient Overlay (10100e) (1e1e1e)
Now by holding Shift key click on the Thumbnail of the Shape Layer and create a new layer select the Soft Round Brush Tool then just make a single click on the selection and reduce the opacity to 15%.
Here deselect the selection by pressing Ctrl + D; create a new layer select the Ellipse Tool and make a shape as sown then apply the following style.
*Gradient Overlay (1d1d1d) (000000)
Again make a new layer and make a shape as demonstrated then add the following Layer Style.
*Gradient Overlay (ffffff) (31d90f)
That’s it you can see dark button and also you can make it as navigation make a few copy of it place it one below the other and make a few changes in color.