Your question is a natural one for newer photographers to ask, but also one for which there is no simple answer as it depends on the photo you want to create. If you're not yet at the point where you understand how the various settings on the camera influence the photo, your best bet is quite probably just to put the camera in automatic mode and let it make the decisions.
If you do want to start taking more control of the photo, the first thing to control is the aperture: a wider aperture (smaller -number) will give you a more blurred background, but if taken to extremes can make you lose sharpness on your actual subject. It's up to you as a photographer to find the best balance.
Unless you're in some fairly extreme lighting conditions, don't worry about trying to control shutter speed and ISO. The camera will do a fine job there.
However: much more than the settings on the camera, you should be worrying about how you arrange the light for the photo. You'll get a much better photo with well-arranged light and the camera in full auto mode than you will with badly-arranged light and "perfect" settings on the camera.