This is the default, built-in authentication module for Wiki.js.
It's enabled by default and cannot be disabled.
There's nothing to configure in order to use this authentication strategy. However, there're extra settings you can enable, such as self-registration.
From the Administration Area, click on Authentication in the left navigation and click on Local in the strategies list.
Users can create accounts on your wiki when you enable the Self-registration option.
Unless your wiki is public and allow anyone to create an account, it's generally a good idea to set an email domain whitelist. Enter a valid domain (e.g. example.com) and press Enter. You can add as many domains as needed.
Make sure to set a group to be assigned to when the user login for the first time.
Click Apply at the upper right of the page to save and apply the configuration.
You must setup the mail SMTP settings (under Mail in the Administration Area) for the registration emails to be sent. Users won't be able to login until they verify their account, using a link sent to their email address.