One product store

Hi,
I have a one product store. Its just one page with a buy it now button which leads straight to the cart page. I purchased this plugin as i thought it would perform an upsell. when the customer clicks buy it now, i would like for there to be a pop up that asks them if the would like to add a bonus earring for $X to the cart. this doesnt seem to be working from the homepage. i do not have a product page which is visable to people. the shopping happens direct from the homepage, stright to the cart. can you help?