App built for container company, app link to online store

I need an android and mac application for a company that sells all sizes and shapes of pop top containers. This company has a high volume of sales and wants to create an app for customers to be able to access the online store at their own time to shop and place new orders. Would also like to increase the online sales of the business as the website has been up and functioning but needs some help with getting the key word search optimization in place and any other strategies for increasing online sales. Most important is the app first and foremost.