How to remove sim card from iphone 4s?

Need to return damaged phone, directions on the return envelope says to remove battery, sim card, SD card, any accessories.
But I have no idea how to do this, please help.

Thanks in advance.

If you look at the right hand side of the phone (screen facing you), you will see a small hole. You should have received a little sim extraction tool with your phone. If you no longer have it an opened up paper clip works just as well. Gently push the end of the paper clip into the small hole. You will then see the top of the sim tray emerge. Simply pull this out and remove sim. The (empty) tray can then be pushed back in.