European Super League - based on the Italian system, so a Premier League, a second league, and three regional leagues.
Use a file installation app such as ES File Explorer to download directly onto your device or on a PC/Mac using your device cable.
The file should download as a .txt file - if necessary, extract the file using 7zip, WinZip or ES File Explorer then copy the changes.txt file.
Navigate to Android/Data/football.manager.games.fm19.mobile/files/installed and Documents/Sports Interactive/Football Manager Mobile 2019/normal. Paste your file in both locations. After this go to the settings and reset your skin cache.
I would recommend starting with Italian Serie A,B,C, England Prem, Spain La Liga, plus the top division from whatever team you want to play, e.g. if you want to play as Ajax, load Holland,