It’s quite simple:

1. Find the free web proxy — list here
2. Look for the “URL” or “website” search box.
3. Enter the URL (www) of the site you are trying to unblock.
4. Click on the submit button.
5. Enjoy your unblocked site!

There is usually several options at the top of the “proxified” page, you can try them and see if it loads the site any better.