Start by doing some learning paths and get to know how Mendix works. This will give you a good baseline of the platform.
After that write down what you need, for example: customers, products, cards, cardentries, orders, orderlines, prices etc. Convert that into a domainmodel.
We can help you with any questions, but you’ll have to built it yourself.
Hi Surya Selvakumar,
If you want to add product to cart follow these steps,
Start with downloading the Base application. This will give you a kickstart as it does contain several entities that you need: Person, Company, Product, Purchase- and Sales-Order, Invoice. Gets you on your way: