With the new store purchases are applied directly to the account you use when purchasing them, there is no code to enter.
If you have the pre-order items in-game then your purchase was successful and there's no real need to worry about it showing on your account page; I suspect that at some time in the future it will.
[center][url=http://forums.lotro.com/showthread.php?18699-How-to-get-help-on-the-Tech-Forums-and-how-to-contact-Turbine][color=gold]How to get help on the Tech Forums and how to contact Turbine[/color][/url]
[color=green]Please reply to the topic or PM me if a solution I posted works for you: The more data I can gather the better I can help.[/color][/center]