use cufft to transform 1D sequence to a Freq Sepctrum with different length

I am using cufft to transfrom 1D sequence,actually, the source code is MATLAB code. In MATLAB the fft transform is very simple.
SO, I have a sequence called X[84], and its length is 84, and I want to make a 4096 point FFT of X[84] ,how can I program with CUFFT? In the guidance of CUFFT, I find this question is not mentioned. Or maybe I didn’t read it carefully.
PLEASE help me!