If you are talking about getting a blurred effect (known as Bokeh, from the Japanese for blurred/blurry) then you need to use a low 'f' numbered aperture, in the case of your camera f2.8.  I am not sure whether you mean blurred effect when taking a macro or a landscape type picture, either way the smaller the number aperture, the more the effect.  Smaller number opens the aperture of your lens wider, higher number, in your case f8, will give a smaller aperture thus leaving more in full focus.

I am sure that somebody will come along and post a link so that you might better understand about depth of field.  This is quite an important bit of knowledge if you want to make the most of your photography.

Also, use the manual modes as opposed to full auto.  Some use 'A' which is aperture priority.  you set the lens aperture and the camera will set the shutter speed.

Using 'S' is shutter priority where you set the shutter speed and the camera chooses the best aperture.

'M' is fully manual, you set both shutter and aperture.

I hope this helps a little.  Take lots of pics at different settings, trial and error is one of the best ways to learn.