The original poster can modify and delete the contents of the post in the Newsboard. 

To modify a post, click on the wheel icon on the left side of your entry. This way, the post's editing field reappears, and all the parameters can be changed. 

To delete the post, click on the 'X' appearing on the right side of it after moving the cursor over it. 

Attached documents can also be deleted from news entries, to do this, click on the 'X' appearing on the right side of the attached documents section.