The help page you are looking for is for the
ec-cart-widget. I’m not experienced with ECWID but I think that “widget” is for placing a separate cart on the header of the page.
It looks like you have an HTML stack that you put a
my-store- widget in. The cart is at the bottom of that widget. But it’s a different cart than the stand-alone one is.
I think you should consider putting that separate cart widget on the page. Website best practices say that most folks look for the shopping art up in the header (top left). I don’t know if the theme you are using has any way of adding extra content to the header.
If you go to this page on the ECWID site, and scroll down to the instructions for Adding a shopping bag to a custom-built website. Grab that widget and place it near the top of the page.