How do these parts come off???

If you can find something made of flexible, thin metal, with three rounded bumps on the top and a slight bend about two inches wide, that's the tool you need. I guess I should go take a picture of my trim tools. I've had good luck with them. A good old fashioned bottle opener works well for a lot of trim too, especially the roof gutter trim. Just wrap tape around the edge so it doesn't scratch.
I'll go take a picture here, stay tuned.