First, place your form fields in a container (usually a div tag) that has the CSS display property set to none. This will have the form fields hidden when the page loads.
Next, you're going to need to write a javascript function that shows the fields and tie it into your link's onClick event.
The javascript function is going to set CSS display property of the container element (the div tag I mention just now) to "block".
This should get you started. I don't use javascript much, so I can't help more on the function.
