So just plug my drone into my computer and open CleanFlight?
The CC3D is a flight-controller which stabilizes your multi-rotor. The board has digital three axis gyroscope and accelerometer chip and small programmable micro-controller STM32.
To that board usually are connected
- Receiver - talks between CC3D and radio you use to control it with sticks. Receiver usually uses special protocol PPM for your receiver I believe, if its FrSky D4R-II
- Electronic Speed Controllers - These control the speed of motors with high voltage, by low voltage commands from your flight-controller, which is CC3D in your case. They also communicated with CC3D special protocol. For example PWMSync, OneShot125, ..etc
There might be more stuff/gear, but this is bare minimum you need to know about at this point, if you are new.
Now, STM32 chip has some memory to run small programs. It runs bootloader which starts actual firmware (software on copter side).
Another important software is the one running on your computer, ground control station (GCS) for LibrePilot or some other tool depending on software you use.
The way firmware on copter and software on computer communicates is usually over USB using special protocol (UAVLink, MAVLink, etc...). So firmware + software on computer must match, otherwise bits of communication might not be interpreted correctly by either side.
To flyYou should know flight-modes that you are going to use and how to arm. This should be straightforward if your copter is configured correctly from the factory.
OtherwiseIf your copter comes not configured, or if you plan on flashing different firmware than it ships with. This is more advanced topic. Because you will have to configure everything from scratch.
What I recommend is checking with CleanFlight configurator or with LibrePilot ground control station, whether either of them shows sings that computer's side tool connected.
In LibrePilot these are green squares in the right bottom corner. You should also navigate to Scopes to see sensor reads in time, when you move copter scope with Gyro states show change, but be careful not to rip-off USB connector while playing like this. Both LibrePilot and CleanFlight have model of copter and scopes which should react to copter movement when you have it connected and it's communicating.
This is the quickest way to determine which firmware it came with. I also recommend sticking to whatever it came with, and once you read-up, then switch to LibrePilot.