This documentation is not using the current rendering mechanism and will be deleted by December 31st, 2020. The extension maintainer should switch to the new system. Details on how to use the rendering mechanism can be found here.
Simply install and enable the module in the backend. A backend user can be configured to add/edit the redirects if needed.
If you used RealURL before you can simply migrate all current redirects to this module simply by using the update script in the extension manager
Migrate RealURL redirects¶