How do you save your contacts to your sim card on a Sony Ericsson?

Go into your menu and select "Address Book." Scroll all the way to the bottom, and there should be an option called "SIM management." Select that, and you can choose to copy contacts to your SIM card, delete contacts from SIM card, or copy contacts from your SIM card.

Note: you must go to the address book through the menu, not by selecting contacts. If you select contacts,you will not have the option to save to SIM.