Work with the Elliptical Marquee tool

Select the Elliptical Marquee tool  (M) from the toolbar. If you can’t find the Elliptical Marquee tool, click and hold the Rectangular Marquee tool () to show the other related tools, and then select the Elliptical Marquee tool.

Specify one of the selection options in the options bar — New, Add To, Subtract From, and Intersect With to get the selection you want. 

Specify a feathering setting in the options bar. Turn anti-aliasing on or off and set the selection style — Normal, Fixed Ratio, and Fixed Size, for the Elliptical Marquee tool. 

Click and drag in the image over the area you want to select. Hold down the Shift key and drag in any direction to constrain your elliptical marquee to a circle. Hold down Alt (Win) / Option (Mac) as you drag to make an elliptical selection from the center out.