How to convert sampled real audio signal to it's IQ components for IQ modulation?
I’ll answer the question I think you’re asking here:

If you have a real valued signal that came right out of an A/D and you’d like to recover signal phase, you can use the Hilbert transform to generate a version of the signal that is in quadrature with your A/D output. In this case, your original real valued signal would be the I component (in-phase) and the output of the Hilbert transform multiplied by j, the imaginary number, would be your Q component (quadrature).

Now if you have some modulation you want to deal with, you would do the IQ recovery first like I just described; once you have that IQ signal you’re pretty much completely characterized the signal, so you can do just about whatever you’d like with it while preserving phase.