If you've really run out of oil you will have a seized engine and a useless car. I assume you have a 'low oil' light winking at you to say 'top me up'. I don't know your specific car but open the bonnet and look on the top of the engine for a round cap. It will probably be metal and may have an image of an oil can on it. Make sure the engine is off before you unscrew this - usually half a turn and it will then lift off to reveal an oily inside. That is where you will put in your extra oil. Use the dipstick to ensure you get the right level. You will probably only need to put in 1/3rd of a litre. If you overfill you will make different problems!
Richard
December 2008