Photoshop cs5 tutorial radial blur

first open aa image,in left panel at the bottom there will be a tool named"quick mask mode".This tool is used for selection.click on this button + brush tool.Suppose in the image there is a girl with a beautiful background,we want the backgroung to be radial blur around that girl.Now paint that girl,after painting,again click on "quick mask mode" button.the area except girl will be selected.Now go to filter->blur->radial blur,inside it click on zoom.Quality-best.Amount-45.press ok.Done