Have you looked here http://www.dlink.com/products/default.aspx?pid=DIR-655&tab=3? If you already tried to set it up, please post what you tried, what the results where, any error messages, etc...
Often when questions like this are posted people either A. Never looked at the instructions or B. Already tried a bunch of stuff so when we start posting answers we get back "I already tried all of this", wasting everyones time.