Well you already know how to get to the block admin so your in the right place, just prolly doing a few little things wrong.
- navigate to the "Add a New Block" area
- Forget "Title" and "RSS/RDF file URL" for now, click on "Setup" next to the "Custom" drop down box
- find the website you want to feed from in the list provided. If the website your looking for isn't listed, find where they feed their news from and add it to the list
- copy the url of the site you wish to feed from
- go back to "Add a New Block" area
- paste the sites RSS/RDF file URL in the appropriate box
- click on the "Custom" drop down menu and find the site name that matches up with the url in the RSS/RDF file URL
- filename = none
- give your block a title
- position your block where you want it on the site
- choose a refresh time
- click the "Create Block" button.
voila
