Well, you have to start by building the wiki. That will be the most significant thing you can do. The more you build it, the more likely (but no guarantee) search engines like Google will suggest it. If your wiki meets the criteria, you might consider requesting a Community Spotlight. Although, I have heard mixed things regarding whether or not Fandom is still taking requests for those. Other than that, you can try advertising the wiki in appropriate places. By "appropriate", I mean places coving a similar topic, where the community might be interested in your wiki, and where it is allowed. Some places just straight-up don't allow you to advertise other sites/wikis.