Installing new online league on a Mac
With your OOTP game closed, the first step is to locate the library folder, which should be under the User section in your finder.
From there go to Application Support > Out Of The Park Developments > OOTP Baseball 18 > saved_games.
Or from the OOTP load game screen, if you hit open folder it should take you to the selected league file, and from there if you right click on the folder and hit 'get info', you can find the path under 'general'.
And then add the folder name (which should contain an “.lg” on the end).
The rest of the process of adding the league files is the same in either a Mac or PC.
Within the LEAGUE.lg (LEAGUE being the name of your league) you can unzip your provided league files.
Among those files there may be a “settings” folder. If not, you must manually create one. Into that folder you must place your provided “accountsdata_gms.dat” file, which is needed for the export/download coordinates.
You should now be set up and ready to go.
Start OOTP, load your new league file. FIRST thing to do would be download the up to date file, which also tests your ability to do that. Then immediately export your league file, again testing that.
You should be good to go!