If you are a registered user, login to your account and go to "Manage My Posts".
If you posted as unregistered user, use the Self-Activation email that you initially used to activate your post.
* If you can't find it, you can have it re-sent here.
Edit your post, make any changes that you need and then click on "Publish My Post." The changes will take effect immediately. Make sure that you refresh/reload your browser to see the changes.
To delete your post, click on "Delete".