I see people suggesting videos, but I would actually recommend getting this trainer chopstick system which enforces correct hand holding position and movement. Once you use this and try swapping with real chopsticks, and compare how your hand moves, you will get the feel of it and have experiential knowledge, which no video nor descriptive-knowledge can give you.
Try it:
Edison Training/Helper Chopsticks for Right Handed Adult
EDIT If you are left-handed, they have a left-handed version: