Whether you want to understand what they are is up to you, you can generate them with the following line or use a lookup table in program memory (table available in link following).
Code:
TwidFactorInit (LOG2_BLOCK_LENGTH, &twiddleFactors[0], 0); /* We need to do this only once at start-up */
Have a look at some of their example code (e.g.
https://ww1.microchip.com/downloads/en/DeviceDoc/CE018_FFT_DSPlib_101007.zip). You can use the above function to create them in RAM, or you could have them defined in program memory (see twiddleFactors.c in the above .zip).