Use plugins to add eCommerce to existing websites and use updated software of the website to add the extension. Now, add a separate solution for business websites to get online sales. This would help offer a seamless experience to users on eCommerce websites. Ask the developers to add the features on the existing website such as shopping cart, payment gateway and other options. The basic features would be accessible for users to use. The designer’s team you hire should know how to include the buy button to help users in online shopping.