The circuit diagram above shows how the components will be wired together. This won't be 100% exact in the actual circuit but it's a very close approximation.
Arrange the LEDs evenly across the two sides of the boards. It's helpful (but not strictly necessary) to keep all the LEDs in the same orientation (all long legs towards one side). Here's an LED layout diagram:
This circuit will be powered by the Adafruit Powerboost via 5V power supply. You can optionally connect a USB battery pack into the Adafruit Powerboost to make it portable. To turn on and off the circuit, you can use a USB cable with a on/off switch.