How to implement the custom field in Magazine Style Post?

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I made a website a week ago and I instaled a template that has a magazine style on page, but I dont't know what is wrong when I implement the custom field for frontpage post. In the exemple post they have the word "Key" and I have the "Name" in stead of Key.(in my post). What means Key? What must be write in this space of Name(Key)?Maybe the name of the post ? For the value I had write : http://mysite.com/wp-contest/uploads/xxxx.GIF ,and nothing happend.