there is no "blur tool", only a blur effect. To make a blur tool, duplicate :DuplicateLayer: the layer with your image on it, then on the bottom layer, apply a gaussian blur (menu -> effects -> blur -> gaussian blur ) with the amount of your choice.
Now, select the clone stamp tool and lower the opacity of your primary color ( set it about 105).
Make a new layer :AddNewLayer: on top of all the others layers. On the blurred layer, click at the center of the image while holding CTRL, then, on your new layer, click at the exact same place.
Voila! you have your blur tool. Hope this helped