Your phone should automatically connect to a network. If it does not, you will have to search for a network manually. Go to OPTIONS>MOBILE NETWORK>NETWORK SELECTION MODE
Select MANUAL then your phone should start scanning for a network. Once it has found one or a few, it will give you a list to choose from. Just select one and see if it connects, if it doesn't choose another.
Just make sure you have a roaming plan with your provider before you leave the US. Otherwise you may not be able to connect and even if you do you won't be able to make or receive calls. If you're using prepaid cards, ask your provider if you can roam with it; I don't know about over there, but here in Asia most prepaid cards can roam up to the value amount of left on the card. If your's can, don't forget to fill it.
