When I took Tiki to the vet, the vet showed us exactly how to do it and what to clip. We have those cat claw trimmers, the ones that wrap around the nail before it clips. That's what she used too.
She said that if they got badly caught, it could rip off an entire finger! Ok, so that was it. I sucked it up.
When I did it myself for the first time, I was SO NERVOUS - quite visibly shaking.
I drank a beer (not kidding).
Tiki didn't even budge. She didn't care. It actually wasn't that bad.
You can do it!