Ok, I'm going to whack a tutorial on how to join the league in here as it is a MASSIVE ballache and took me and the Fagcat about 20 mins to figure out!
From the main menu, go multiplayer, internet leagues and then either sign in or create a new account. You'll be taken to a screen that has 4 quaters. The one we're interested in is the top left at the moment which is where you can manage your teams and leagues. Hit the "Create a Team" button and make your team. For the purpose of this league, I'd like everyone to start a new team.
Once your teams made (it's the exact same process as in the single player so I won't go into detail here), you need to quit the public league as each team can only be registered in one league at a time. To do this, from the main screen (the one with the 4 quaters remember?) you need to highlight your team in the top left section, and then in the top right section just hit the "Quit League" button. Job done.
Now, to add yourself to the WDG League you need to hit "League Search" in the top right section to get a list of all the active leagues. Filter by Coach and look for me, highlight the league and hit "Apply for the League". I will then accept in due course

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Also, if you want to get some practice in against each other online you both need to have a team in the public league and then in the bottom right hand quadrant of the main menu there is a "Search Opponents" button with 2 wierd symbols before and after it. SELECT WHICH TEAM YOU WANT TO USE IN THE PRACTICE MATCH BEFORE ISSUING THE CHALLENGE! Hit the one on the left to do an advanced search, search for the coach you want to play and issue a challenge. Boom.
I've never come across a more obnoxious interface, if you need any help getting anything set up, hit me up on Steam and I'll talk you through

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