Ok here you go.
Note this is a different technique as i said earlier both ways work but for an even border this way is better.
First open your picture
i choose this one i made a while ago
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Then if the layer is locked which it probaly is unlock it by clicking the lock on the right, then name it whatever you want.
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Select the Elliptical Marquee tool.
Drag a marquee selection around the area of the photo you want to keep.
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Click the "Add layer mask" button at the bottom of the layers palette
Then you should only get ur selection.
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Next i added a background so you get to see the next step more clearly.
To do this click new layer make sure you put the layer below you picture
Then use the paint bucket and fill the background whatever colour you want.
I just choose white.
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Click on the layer mask thumbnail in the layers palette, this is the picture which shows the cirle in the button right.
Then go to Filter > Blur > Gaussian Blur and make sure the Preview option is checked so you see what you result will look like. Adjust the radius until you are happy with the amount of fade and click OK.
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And your done
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If you are having any problems just ask and i'll get back right away