The world won't be starting until the time announced, 10am UTC. You're too early. When the time comes you go to the change world option on the front page (after logging in) and choose the new world.
And where i can find that button? "change world option" After loging i go directly to last played world. And in the game i only can switch between worlds iam already in.
This is a shortcut to where you're taken with the 'change world' option: https://gamecdnorigin.alliances.commandandconquer.com/WebWorldBrowser/index.aspx?langPreferred=en-US
There will be a list of all your worlds plus a "start new game" choice. Click on that then choose the world you wish to start on (it should be top of the list).
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