Drag out the ellipse with elliptical marquee tool which you will find in the tool box
Go to Edit menu>Stroke(outline)selection. Enter the value for width , color, place it inside
It's a good idea to open a blank layer at the top and put the sroke on this layer.
Press CTRL+D to get rid of the marching ants
The only elipse tool I can find is in the custom shape box. When I use this the stroke command in the edit menu is unavailable. Could you please tell me where I am going wrong?