The SIM card is used to store information and it is well hidden under the battery. It is very easy to open once you know where it is.
Remove the back cover plate of the phone. To do this press down the lock as you slide the cover toward the bottom of the phone.
Once the back cover plate is removed, the battery should be exposed. Remove the battery by prying it out. This can be done with your finger-nail or a prying tool.
Once the battery is removed, the SIM card compartment will be exposed. Pry the compartment open as seen in the figure. This can be done using your fingernail or a prying mechanism.
Once the SIM card compartment has been opened, insert the SIM card into the slot provided on the left side.