You can do it 2 ways:
Shop IntegrationIf you have created items on your home page then you need to set them up in the
shop under 'Items' -> 'Create item'.
When you have done this, go to 'Publish shop' -> 'Shop integration' and get the
links to your item.
Follow FAQ: How to include the links in my HTML pagesYou can proceed in this way with every item in your shop.
Cart/Basket IntegrationWith this you are only using the cart feature of 1&1. You are creating the
items in your home page. Follow FAQ: Sample Cart/Basket integrations.