You can add the preorder service to your account by entering the registration code you get after you enter the pre-order code. If you have the PC version, launch the client and it should ask you for it. If you have the PS3 version, redeem the code through the PSN store. Afterwards, when you login, it will ask you what you want to add to your account. Pick the preorder one (it'll also say your pre-order bonus items will be added) and you should be able to download the patch.

If you've already downloaded the patch but still aren't able to see any updates to your account, I wouldn't worry too much about it.