1.The first thing you have to do is, click the selection tool that looks like this. Now its also important that you have the right settings, set them to the same as me.
Feather at 20% is important !

2. Mark out on the picture on the part you want to cut out. When making a circle, start in the center.

3.You now have to copy where you have marked, press CTRL + C and afterwards CTRL + V And the part you marked will appear in a new window with the feather border.

4.Save it or add the effects you want and then save it. Hope you understood ! ;)

Here is how it is looking with the "feather border":