You need to open the forum tools.
This codex article explains how: http://codex.simple-press.com/codex/faq/problem-with-post-edit-buttonow-to/problem-with-post-edit-buttonow-to-delete-a-topic-or-post-and-other-tools/
Yes, but I can not click on the button that appears! Click and then nothing happens …
http://caponier.ru/forum-caponier/8750440
Actually none of your forum popups are working and possibly other aspects as well.
Basically your site is generating javascript errors which is stopping the jQuery library from functioning correctly. the problem is I do not know the cause – at least it is not obvious. Your scripts seem to be loading OK and are all from good sources. But you do have a large amount in in-line scripting taking place.
Sadly – probably the only way to work out what the conflict is is to try deactivating plugins one at a time until things work and then we can more easily diagnose the problem. The same goes for the WP theme which is sometimes the issue – brifly switching to the Wp default theme can tell whether it is a theme component.
Afraid I can’t think of any other way when so much script is being loaded.
Checked. This is a problem my theme. 
This is very bad news – most recently changed his theme. 
In another theme it works correctly…
I do not know what to do now …
Does you WP theme have options so that you can turn scripted components on and off? It is largely a matter of elimination to find out exactly which script is the source of the conflict…
Well I was only asking of your theme had optional components hat you could turn off…