To dial a country outside of the United States, first dial 011, dial the country code, then dial the area code, and finally dial the phone number. Country codes and area codes may vary from country to country, so you need to ask your service provider.
Double check with your provider to ensure that the procedures to dial from a mobile phone are the same as from a land line. Also, consider that the price to call internationally from a mobile phone may be more than from a land line. If you plan to call internationally frequently, you may wish to consider an international long-distance plan.