If you see them through the viewfinder then it is either dust on the viewfinder or on the mirror. Try and either blow it or brush it out. I wouldn't recommend blowing inside the camera body, as you will probably just end up blowing the dust closer to the sensor. Hold the camera upside down (so that gravity pulls the loose bits out of the body and not backwards towards the sensor) and use a lens pen brush on the mirror to loosen any dirt and let it fall out.
If they are also showing on photos, then the sensor will need a clean. You can do it yourself with some special kits, but I'd rather leave it to a professional to do as you can easily make it far worse too.
Another tip for cleaning, always be as gentle as you can be. I managed to remove some of the anti reflection coating on the rear element of a rather expensive lens when it was only a couple of weeks old when I got carried away with a microfibre cloth. I couldn't see the difference in any images, but I still felt pretty ill when I realised what I had done.