Breed a Fiddlement with any compatible Light Island monsters in the breeding structure
Use a level 4 or higher Fiddlement for the best chance
Keep trying until you get the Rare Fiddlement, since breeding is chance-based
Make sure Rare Fiddlement is available on Light Island during the current event or rotation
If Rare Fiddlement is not currently available, wait for its return before breeding
Check the in-game breeding combinations for the exact current pair if the event requires a specific recipe