request to inform me about how to edit an ellipse shape with pen tool

If you are dealing with a pixel layer as Dag has said, then if you Ctrl click it's layer thumbnail to load it as a selection, you can then use this button at the bottom of the Paths panel to turn it into a Workpath.

Best practice from there would be to make it into a shape layer, but much easier to start again and use the Elliptical Shape tool.  I have a feeling that is what you have done already, and that it is just your wording that has confused us a bit.   If we are not getting it, just keep asking.  It costs you nothing as we are happy to help.

I have drawn an ellipse with ellipse marquee tool

By @samitali

The elliptical marquee tool is a pixel tool, making a pixel shape.

It cannot be edited with a vector tool like the pen tool.

To do what you want, you need to create this as vector data from the start, using vector tools. It will be rasterized to pixels on output, though.

@samitali I'm not sure that I fully understand what you're trying to achieve, but with the Direct Selection Tool you can just drag the top centre point down, holding shift will keep it aligned