I struggled with inlays for a while conceptually, same place that you are now. You might find this helpful, I did a detailed write up on how I made it all work.
There are a few other good articles out there too to get started. @WillAdams just posted this one with CC instruction:
and this post has a much better illustration that what I did
You’ll see there are a few different ways to accomplish this depending on your software and workflow, but they all end up with basically the same outputs. Go with what works for you. Hope those help you get started, once I figured it out I went on a tear making inlays out of all kinds of things for the holidays.
