My workflow is to create in Illustrator, import that AI file into Vectric VCarve, create all my cutting paths there & export the .gcode file(s), then use Universal GCode Sender to send those files to the XCarve.
I strongly recommend VCarve. I limped along for a bit using Inventables Easel software but after seeing VCarve in a CNC class at a local maker space, I saw that it’s like comparing MS Paint to Illustrator, a black & white 80’s TV to a new smart tv, or a school lunch to a 5-star meal. VCarve isn’t cheap but they have a 30-day free trial to see what it’s about. Definitely look for some tutorials. VCarve Pro can import your .stl files, but path generation won’t necessarily be automatic.
If you want to try Easel to start since it is totally free, you can create in any program that exports an SVG file, create your cutting paths in Easel (more limited than VCarve) and send to the XCarve from Easel. VCarve will also import SVG, but since it loves AI files, I save myself that step.
Universal Gcode Sender (UGC) becomes the software interface with the XCarve. Some use Chilipeppr. If you use Easel instead of VCarve, you don’t necessarily need to UGC or Chili. (UGC, Chili & Easel are all free) Technically you could create your cutting paths in Easel and send them to cut using VCarve or Chili if you had your own reasons.
Hope that helps. It definitely isn’t a straightforward process andI had the same questions. But this doesn’t even go into things like when to use different types of bits, what different cutting terms mean, etc. I got a TON of good info from the CNC class I took at the local maker space - I’d strongly suggest looking to if there is one in your area.