Login to Bongo4U Admin Mode and go to the page on which you want to make changes. Click on that page's link in the navigation to get to the desired page.

Once you are on the correct page, locate the block that contains the content you want to delete. Hover your mouse over the "Block:" link for that block and the Block Menu will appear.

If you want to delete some of content from within this block, then click the "Edit" link on the Block Menu, update the block to remove the portion of the content that you no longer want, and click the [Save Changes] button.

Or, if you want to delete the entire block, including all of its content, then select the "Delete" option on its Block Menu. There is no undo.