How to edit Forum Headline in this forum?

[Gast]

every posting has his own title and it's possible for everybody, to change this title in his post, so that everybody found a [SOLVED] for this theme

time's to edit postings: 5 minutes without any information, 15 minutes with information about the last changes

[Topiax]

In many forums it is possible to edit message headline: eg. adding [Solved] to the headline after the solution has been found. How is this done in this forum (WebsiteBaker Community Forum)?