I'd still do the first tutorial above, so you can understand how to use VCV Rack, but here is a small tutorial (10 minutes.) That will help you understand what's going on under the hood of your favorite FM synths. He doesn't do this in the video, but I would attach the output to the oscilloscope module to get an intuition for why certain parameters affect the specific harmonics that give FM its characteristic sound.

Your FM synth at home is 100x more time complicated than this patch you build but if you grok what's going on here, you should have a better idea of what going on in your other FM synths.

https://youtu.be/gzWFunWNTjQ?si=veuGdCTc1gETntO3