If you are the commissioner, you have to put the zip or archive the file and put it on your website in a directory somewhere. Then create a link on the front page of your league website so your league members can simply click that link and download the file. Then they unzip it into their "saved_games" folder and start up the game.
EDIT:
this article was originally written for OOTP 6.5 but the principles are the same for any version.