Sign in with your email and the one-time code sent to it. The same account works in the launcher and on the site. The launcher downloads the client or checks files you already have. When it finishes, choose a server and start playing. Your profile contains your UD balance, inventory and mail. If you already have an account, use the same email.
From email to your first match
One email connects the launcher, game and profile. Here is how to sign in.