You will need to contact support by raising a ticket with the thread link and your revised BB code, which you send using Pastebin.
Thread edits are charged at $30 per thread, you can send payment via PayPal to firstname.lastname@example.org. Make sure you put your user ID and thread link in the PayPal comments.
Please ask if you wish to pay another way.
Once we've verified the payment (which can sometimes take up to 48 hours), we will make the changes and you'll be notified immediately.
Find out more information on editing your threads.