From Online Manual
Often posts are modified. Usually a forum will give permission for all members to edit the posts that they made, and moderators will be able to edit everyone's posts including their own.
There are two methods of editing a post, the "normal edit" directs you to a posting page where you can edit the post. "Quick Edit" allows you to edit the post inline, but you will not see the buttons for automatically placing Bulletin Board Code in your posts and will need to manually enter the Bulletin Board Code in your posts.
Normal Edit: To modify a Post or thread, click on the button that says "Modify". Make any necessary changes and then click "Save".
Quick Edit: You can perform a quick edit without refreshing the page by clicking on the pencil on paper icon located at the right of every post. This will popup the post box, once you click on the "Save" button you will see the change instantly.