How do I create a diffraction pattern for a DNA particle?

I know the diffraction cross-section of the DNA double helix, which is a function that is proportional to a series of bessel functions squared. I want to project the diffraction pattern onto an image to create the characteristic diffraction pattern, but I do not know where to go from here. I understand that I need to create a function that is a probability density of the x-ray particles at a certain wavelength, but then where do I go? Thanks!