i just went to paypal.com and logged in, then went to mercant tab. when the page came up the first thing you see is add to cart button. when you fill out all the information and options that you are looking to create, then they will give you a code. copy and paste this code into a html box found on the left side of your builder. why not publish what you have so far so we can see the problem. you can see how i used the pay pal on a site by clicking on this link:
www.scanportonline.com/barrettes.html
the code you get from pay pal will include the continue shopping option. just try one of the buttons. if you try to use the pay pal buttons from the builder you will not get the continue shopping option.
if you need more help you can contact me through my website and i will walk you through this.
hope this helps,
mrmagoo144
www.videopostcards.info