As an example, here are instructions on how to switch off the News aggregator. Other blocks can be switched on and of accordingly.

1. Click on: My account
2. Click on: Edit
3. Scroll down to: Block configuration
4. Remove the check mark from: News aggregator
5. Remove the check marks from the three news categories: Elephants category, etc.
6. Scroll down further, to the end of the page.
7. Click on the [Submit] button.

If you want them back, or just one of them, you can go through this procedure again and enable whichever you like.