From Online Manual
There are two ways to delete posts:
Deleting an Individual Post
To delete an individual post, locate the post in question and click the "Remove" button located on the top right.
Deleting Multiple Posts
In order to delete multiple posts at the same time, you first need to enable checkboxes for quick moderation. Go to Profile > Modify Profile > Look and Layout. To the right of Show quick-moderation as, you will see a drop-down box. Select the checkboxes option here.
Now, go to the posts to be deleted and check the box in the upper-right hand corner of each post that you wish to delete. Then scroll down to the bottom of the topic and click on the button Delete Selected.
You can remove an entire topic, including all of the replies, by going to the bottom of the topic and clicking on the "Remove Topic" button.
Restoring Deleted Posts and Topics
Deleted posts and topics can only be restored if a recycle board has been created. Moderators should ask their forum administrator whether a recycle bin has been enabled.