problem in making article featured?

i recently install wordpress theme to mywebsite at gointernetwebsite.com it contains a featured article
i want to make an article featured so i read readme page for that theme and i do what they ask me here is what they say exactly on how to set an article featured:

2. How do I add the thumbnails to my homepage?

Quadro utilizes a script called TimThumb to automatically resize images. Whenever you make a new post you will need to add a custom field. Scroll down below the text editor and click on the “custom fields” link. In the “Key” section, input “Thumbnail” (this is case sensitive). In the “Value” area, input the url to your thumbnail image. Your image will automatically be resized and cropped. The image must be hosted on your domain. (this is to protect against bandiwdth left)

You will also need to add a second custom field for your featured articles with a Key of “Featured” and a Value of the image URL.

Important Note: You must CHMOD the “cache” folder located in the Quadro directory to 777 for this script to work. You can CHMOD (change the permissions) of a file using your favorite FTP program. If you are confused try folowing this tutorial. Of course instead of CHMODing the template folder (as in the tutorial) you would CHMOD the “cache” folder found within your theme’s directory.

i do that but it appears that image is not loaded see the website

why that occur?
how can i resolve it?

plz help me