If you want to stack a shield on top of the FONA Shield, you'll want to pick up some stacking headers and use those instead of the plain header shown here!
Wanna stack? This tutorial shows how to use the plain header to connect to an Arduino. If you want to use stacking headers, don't follow these steps!
Check polarity for the battery!
Snap the uFL connector on, it will click when placed properly
You must insert a SIM card to do anything but the most basic tests. FM radio does work without a SIM but of course you cannot send or receive texts, calls, etc!