Add to Cart button on pop up page

[Tezzflyer]

I am sure I have seen the answer to this on the forum somewher but I just can't find it!
Can anyone tell me how to get an add to basket button working from within a popup page.
I have inserted the button into the layout but now I need it to work!

URL is

http://www.stormguardrainwatersystem...ater_Pipe.html

any help much appreciated
Thanks
Terry

[RuralWeb]

Just select the extinfo with add to cart layout in design options