Now that everything is connected together, there is only one thing left. Place the battery near the PDB and connect the two T connectors with caution. Note that at this point your quadcopter is not ready to fly at all. You have to pass the calibration and the pre-flight testing list before you can actually fly your vehicle. The point here is just to make sure that everything is working.
A well-built quadcopter should have beeps from the ESCs and a red-black LED blinking at the flight controller. If you can hear the beeps and see those LEDs, you did a great job!