Some question about OFDM

hello everyone
i would like to know how to change the number of sub-carrier ,
another question how to change the modulation for ecch sub-carrier ?

i have already known that if i want to reconfigure the modulation for
each sub-carrier (bit loading for OFDM), may be
requied reworking .so hwo to edit ?

I appreciate any of you help and I was wondering if anyone has already
impelemented such a system and some code is publicly available.