How to link "Add to Cart" button on web page

I would like to add a "Add to Cart" button on my regular site next to the area that describes the product. I copied the code from my Zencart page and get the button on the page but cannot get the button to work.
The page I am adding the button to is https://www.everbritecoatings.com/jewelry2.htm.
I have searched the help and the forums and have spent hours & hours trying to figure this out.
I would really appreciate any help.
Thanks very much,
Teresa

Zencart doesn't really work that way - it's not meant to be a add-on cart script for an existing site.

If you do make the link work, if a customer who is logged in to Zencart moves from your main site to Zencart and back again, his Zencart session may be messed up.

I tried doing something similar. I put the product_info page inside of an iframe on my html site. When the user clicks a thumb on the html site it opens an iframe with the product_info page above it. That feature works fine, but the problem I am having now is that the when the user clicks "add to cart" it opens up the checkout inside of the iframe. I want the add to cart link to open a new page. Anyone know what part of the code controls where the add to cart button links to? I want to change the target for the add to cart button to _top.