I found a 12 sided object that I really like, but I have no idea how to make the rim that is on there, and I am wondering if anyone could show how to achieve that same result of the rounded rim in the screenshot (doesn't need to have 6 even segments around it), so that I could add additional rims around the object (for example, if I wanted to add another rim above or below the original?)
Start with a loop cut around your object:
Give the loop some thickness by beveling it with Ctrl+B. Select the new faces around the edge (but not on the existing extrusion), and "extrude faces along normals".
Select the top and bottom edges of the new extrusion:
Then use Ctrl+B to bevel again, this time scrolling the mouse wheel to add more segments. Move the mouse to adjust the bevel until it looks right.
If you're concerned about clean topology, you may need to add some new cuts into the extrusion that was there before the loop, and remove the new overlapping face created by the extrusion, but otherwise it should be fine.