These steps should cover it all (minus texture making).
1. Clone a new basegame ring
2. Export the .blend
3. Open and import your ring mesh
4. Arrange in the same place as the other one (or wherever you want)
5. If your mesh doesn't have a UV map yet, do that (you can find out how to do that on youtube), and call the UV map UV_0
6. Move your ring's UV map (and make it smaller) so it fits in the ring area -
i.imgur.com/35eI9te.png, u can put this image into blender on the UV editor so it's easier to follow
7. Transfer the weights from the EA ring to your ring, tutorial -
sims4studio.com/thread/81/weight-transfer-blender8. Add a new UV map to your ring called UV_1, and transfer the UV_1 from the EA ring to yours, tutorial -
sims4studio.com/thread/13309/smooth-weight-uv-1-transfer (ignore the subdivision part cus that's for clothes)
9. Make the vertex paint for your ring green -
sims4studio.com/thread/2479/vertex-paint-sims-4-mesh (just get the green colour and use shift k to make it all green).
10. Delete the EA ring, and change the cut/meshgroup number for your ring to be 0000
These steps pretty much apply for creating any type of CAS content.
If you need anymore detail on a step feel free to ask.