Making my own tweaks to Football Manager 2022 Data Update

How do I make my own changes to the file I downloaded from the site (Football Manager 2022 Data Update), I need to add a few personal tweaks but cannot find how to save it from the pre-game editor.

open it in the editor and make the changes you want, then save the changes

NB if it is an xml file  you need to use import to open it, export if you want to keep it in that format

if you want a fmf file you use save, but then you will have 2 files so delete the original xml one 

There's no need to edit our file, you can just create a seperate file and use them both together.

The files are loaded in alphabetical order so just make sure yours starts with a Z or something.