Also as Outline by Tihomir above, you can alternately go to 'FILTER / BLUR / LENS BLUR. A new window will pop up. Click on the part of your image that you DO NOT want to blur. You will see the Numbers above the sliders or the right side change. They tell you your depth of your object. Then adjust the sliders below to the desired blur effect you want. After a couple or three times you will know about how much to Adjust the DOF Blur. 
You can find more about it CLICK HERE
Hope that helps.

I would rather be Politically Incorrect,
Then have Politically Correct-Incorrectness!!!