You can only edit your posts for 24 hours after making them. If you need to make an update, I suggest you either PM the Minion of your section with the BBCode for your ENTIRE thread so they can update it for you. If you do not have a minion, then press the report button on your thread requesting an update with the BBCode included in the report.
Put your thread contents (BBCode) onto Pastebin.com - #1 paste tool since 2002! and include the link. This makes it much easier for us to update it for you.
To get your current thread contents, press the reply with a quote button and then remove the quote tags. Then copy the remaining contents of the message.
Hopefully this explains it well enough