That code I provided using EJEJC_show() is only if you wanted to use the cart's lightbox overlay to display other pages unrelated to the cart; that code is not necessary just to use the cart itself in your site.
Once you set up your products in E-junkie Seller Admin, we provide you with ready-made HTML codes for your cart buttons. Each product gets its own Add to Cart button code, and you would also have View Cart code that is unique to you but the same for all your products -- just make sure you paste one block of View Cart code on every page, as that code manages the cart overlay inside your page. You would simply copy the codes from us and paste them into the HTML source of your own Web site pages, wherever you want our buttons to appear among your own layout, text and images.
Buyers would click Add to Cart for the product(s) they want, and then they can pick what quantity they want to order in the cart itself, if you enable "Let Buyer Edit Quantity" in the product's settings. If you want to offer a selection of options such as size, color, etc., you would configure the product using our Variations/Variants feature, which would add option menus and/or text boxes to the Add to Cart button:
Our system is designed to be really quite straightforward to configure and set up, and you have a fully-functional 7-day free trial period which begins as soon as you register for an E-junkie login. Our Getting Started help page is a good place to begin setting up your E-junkie service: