The first thing to do is to open up your aperture. Find your setting which does that and use the lowest number possible. I see your lens has a maximum F2.8 which is pretty good.  That will help isolate the subject from the background.  For further assistance in doing this, physically move your subject away from the background to get it easier to blur ;)

Secondly move closer to your subject with a wide angle and the background will be even more blurred - this is because at a closer focusing distance the effect is multiplied. Think of any macro photos you might have taken/seen... the bug might be in focus but the leaf isnt...

Hope that helps - for learning more about why rather than just understanding how to do it check out this wiki

"In every colour, there's the light.
In every stone sleeps a crystal.
Remember the Shaman, when he used to say:
Man is the dream of the Dolphin"

Rich Meadows Photography