Activate forum moderation
From the menu, Add-ons > Forum > Options tick the box titled Forum moderating. In doing so you can select all the site members or a specific member group that can moderate the Forum.
The moderators can then edit, delete, close, and move messages or threads.
Once you have ticked the box to allow Forum moderating you must select a member group. If you have not yet made a group please follow this tutorial to create a member group.
As always hit save!