Teaching a skill involves training time.
1. Do it yourself first with the child watching. Perhaps more than once.
2. Do it while you tell the child each step you are doing and how it's done.
3. Have the child do it while you tell them how.
4. Have the child do it while you watch. Answer questions if they ask. Coach if they need.
5. Have the child do it by themselves.
6. Inspect their work.
7. Repeat instructions in areas where training hasn't taken effect yet (starting with step one and repeat steps if necessary.