Open the back cover and remove the battery. Insert the sim card on either of the two slots. Please note the orientation of the sim card. There are two slots, one goes face down, the other one goes face up. It uses two full size sim cards.
In the Settings Menu you have the option to activate either SIM 1 or SIM 2, the SIM activated will be the SIM (phone number) you'll use until you choose to activate the other one. Even though it can hold 2 SIM cards at once you don't need two, if you have 1 ISM card you can still use this phone.
As Byron stated, phone, wall charger with USB port, USB cable (use with charger, or as connection to computer), earphones. All of the accessories are pretty generic. Also a manual that is very basic, not really much help.
On top of the phone, next to the charging port there is a small gap, with one hand grab the phone and with the other by using your nail or something flat and pointy that will not damage anything, push the backdoor away from the phone and just slowly remove it all.
It will feel like it will brake, but it won't. Just do it slowly.