Google "sensor cleaning" and you will find plenty of info on how to do it yourself. You may be able to use a blower bulb to blow the dust off but as D-50 said, be careful not to get more on the sensor. Always do it in a clean room...set it to cleaning mode (with full battery)...turn it open side down and gently give it some puffs of air.
If the spots remain, you may need to use a sensor brush or cleaning pads etc. You can learn to do it from web sites...but maybe seeing someone do it for you, would be the best way to learn...if so, ask at a good camera store.