If your account was flagged as a protential 2nd account you will need to vet your account from an LG Staff Member.
What do I need to vet my account
If you are an xbox member, and you are "Gold Sharing" you will need to provide a photo proof of your xbox showing your account and the account of the Gold Member you are sharing with . Example http://i.imgur.com/OevjhpE.jpg
If you are a PSN User - you must provide information on any related users you might be connected too
Who do I contact to vet my account
This depends on which league you are planning on joining. Each League may have its own member to vet users, so please read this list carefully. Once you've identified a user to contact, click on their name to send them a message