You don't send invites to a new account, you actually add the new account to the group, it will be automatically added if the groups doesn't require admin approval, or it will be pending and waiting for admin approval if the admin of the group set it like that. So in some of the groups you'll have immediate access, in some you need to wait for approval. One thing i forgot to add, the two accounts ( the main one and the one you're adding to groups) need to be friends, you can unfriend after you added the second account to all the groups.