1. With your 3D disconnected, download and install the Midi Fighter Utility
2. Connect your device and make sure the firmware is up to date (support was designed for firmware of 30 May 3013).
3. While still in the MF Utility click on "Tools > Import settings" and navigate to "C:\Program Files (x86)\Image-Line\(FL Studio)\System\Hardware specific\DJ TechTools Midi Fighter 3D\FL Studio.mfs"
4. Close the MF Utility and open FL Studio.
5. Open the MIDI Preferences and make sure your 3D is detected and enabled. It should look like this:
6. Close the preferences.
7. Click the top left side button and the LEDs should turn red showing the unit is in keyboard mode.
If all you want to do is trigger drum sounds with it you can set up FPC for that as shown here.