For details on earning the title for yourself, see RuneScape:The Wikian.
[FAQ] • [doc]
Wikian book detail

The Wikian book is a unique item used to grant the title [Name] the Wikian. It can only be obtained by being directly added to the player's account by a Jagex Moderator.

The title is granted by using the book on the other player – similar to inviting to a clan. This prompts a confirmation message, and once confirmed the recipient is immediately granted the title. Upon receipt of the book, the title is granted to the owner (as the book cannot be used on oneself).

Even though only one person can own this item it is possible for the title [Name] the Wikian to be given to multiple players, of which the list can be found here.