A version of the below with screenshots is available on the sortitoutsi forums: https://sortitoutsi.net/content/56768/fm2021-licensing-and-real-name-fix-file-v01-beta-for-fm21-beta-not-released-yet

Step 1:

Go to: 

(for PC Steam users)
Program Files\Steam\SteamApps\common\Football Manager 2021\data\database\db\2100
AND
Program Files\Steam\SteamApps\common\Football Manager 2021\data\database\db\2101
AND
Program Files\Steam\SteamApps\common\Football Manager 2021\data\database\db\2111
AND
Program Files\Steam\SteamApps\common\Football Manager 2021\data\database\db\2130

(for PC Epic Games users)
Program Files\Epic Games\FootballManager2021\data\database\db\2100
AND
Program Files\Epic Games\FootballManager2021\data\database\db\2101
AND
Program Files\Epic Games\FootballManager2021\data\database\db\2111
AND
Program Files\Epic Games\FootballManager2021\data\database\db\2130

(for Mac users)
USERNAME \ Library \ Application Support \ Steam \ SteamApps \ Common \ Football Manager 2021 \ Data \ db \ 2100
AND
USERNAME \ Library \ Application Support \ Steam \ SteamApps \ Common \ Football Manager 2021 \ Data \ db \ 2101
AND
USERNAME \ Library \ Application Support \ Steam \ SteamApps \ Common \ Football Manager 2021 \ Data \ db \ 2111
AND
USERNAME \ Library \ Application Support \ Steam \ SteamApps \ Common \ Football Manager 2021 \ Data \ db \ 2130

You can find these folders by clicking, in the Finder, the Go menu in the menu bar, then choose Go to Folder and type the folder path name (obviously inserting your username), then click Go.

(Mac Lion users)
use the above path, but the Library folder will be hidden. Use this link to learn how to display it: http://osxdaily.com/2011/07/04/show-library-directory-in-mac-os-x-lion/






Step 2: 

Delete the dbc, edt and lnc folders from the folders above, but leave the 21xx_fm folder alone. I repeat, you must DELETE the dbc, edt and lnc folders. Replacing/merging won't see all the changes implemented





Step 3: 

Copy the dbc, edt and lnc folders from this download into the folders mentioned in step 1.





Step 4: 

Go to:
(on PCs)
Documents \ Sports Interactive \ Football Manager 2021 (or your user data folder if you have changed the path)

(on Macs)
Users/YOUR Mac USERNAME/Library/Application Support/Sports Interactive

By default this folder is hidden, so to access you need to do as follows:

Open Finder
Click ‘Go’ from the menubar
Press and hold down the ‘Option’ (Alt) key
This will bring up the ‘Library’, click to enter then go to ‘Application Support’ -> ‘Sports Interactive’ -> ‘Football Manager 2021'





Step 5: 

Open the folder named "editor data" contained therein.





Step 6: 

Keeping the folder in step 5 open, go back to the file you downloaded and copy the 10 files included within the editor data folder.






Step 7: 

Paste these 10 files into the folder mentioned in step 5. Accept any overwrite prompts. If done correctly, the path and files should look like this: https://imgur.com/sPpeRLc





To make sure the files have been applied correctly, go to the Champions Cup and EURO Vase in your saved game, and they should be renamed to Champions League and Europa League respectively. If you are in the middle of a save-game, Japanese national teams will be populated in the next instance that players are called up, and not instantly.

If you're confused at any step, please watch this video: http://www.youtube.com/watch?v=rBPUdZU-Gfo&hd=1

Although it was created for FM13, the steps are broadly similar.