You can find code examples that compute transforms in the Fourier Transform Functions Code Examples.
Usually you can compute an FFT by five function calls (refer to the usage model for details). A single data structure, the descriptor, stores configuration parameters that can be changed independently.
The descriptor data structure, when created, contains information about the length and domain of the FFT to be computed, as well as the setting of several configuration parameters. Default settings for some of these parameters are as follows:
Scale factor: none
Number of data sets: one
Data storage: contiguous
Placement of results: in-place (the computed result overwrites the input data)