XF 1.4 How to create a custom 404 Error page

[Exemption]

Greetings again

Today I wanted to setup a custom 404 error page when a user enters something wrong in our domain (http://mysteriarealms.com) but as of right now, XenForo brings up an error page:

When I want a Custom 404 Error page Anyways if you guys can let me know how I can set one up, feel free to comment ​

 

[Creaky]

You could use this add on, never used it myself though

https://xenforo.com/community/resources/goodfornothing-four-oh-four.767/