I got this by playing the Scottish league. I chose Celtic (Glasgow greens) and swapped out the other teams with the teams in Div 3 in Scotland.
You highlight the teams you want to swap out in black from the prem and then select the replacements by making them red in Div 3
Make sure you make your team light blue/purple to become the coach then just simulate the season.
Just select play match - result - view result -exit
Then repeat until season is finished.
You should also get the CHAMPS ach too.