Start by placing the shield on top of an Arduino (any will do) and threading the four long stacking headers through so they plug into the Arduino headers.
Pull on the shield a bit so that you get a few mm of gold pins showing, then flip it all over and place on a table as shown. It should sit nice and flat
Tack the outer pins of each stacking header. This way they'll be aligned right.
You do not have to solder all the pins! Just do 2 pins per header
Check your work, especially the power (5V) and GND pads! Make sure there's no bridged solder connections
Plug in your battery into the JST connection, you're ready to go!