If you know the NPCs name, then feel free to simply search is in the World anvil search bar. The search bar even has auto correct if you aren't 100% sure on spelling.
2. Search in categories
NPCs can be found in a few places across World Anvil depending on a few criteria based on when the NPC was encountered, what it is known for, and how common the character is across multiple campaigns. The following flowchart is based on the categorization criteria used by the worldbuilders of The Leyden Nexus, so it should act as a consistently reliable guide for finding the NPC you are looking for: