You can only edit a message you've posted if you are a registered user of the Forums. Only moderators and administrators can edit general users' messages. Either post a correction message if you typed something incorrectly, or ask a moderator to change it. Registered users are users that have registered their username with the Forums, and use a password to identify themselves. They also have a profile page with their full name, homepage, etc, and they can edit their messages after posting them.
General users are users that post messages on an ad hoc basis.
EngNet's Forum Watch feature is a service that will keep an eye on the forums and topics that you select, and then email you whenever someone starts a new discussion in them. This means that you don't need to continually check the site to see if there are new discussions of interest. To use Forum Watch, you need to be a registered user .