Cup consists of three phases, of which the first one is basically qualification phase for lower tier teams. And is played in first half of the season. The main tournament is played in second half of the season.
This is my first custom database, simulated 5 years into the future and everything was working.
How to compete in the Balkan cup on FM18Move the downloaded .fmf file to your "editor data" folder.
By default this is located at:
Documents > Sports Interactive > Football Manager 2018 > editor data
If that folder doesn't exist, you need to create it yourself.
Start a new career game with this database enabled.