Every webpage should have a primary action it wants users to take. A homepage or landing page has the very clear purpose of getting users to take the next step in buying, which usually means searching for products.
There should be an obvious link or button which takes users to search. It should be presented in a contrasting colour that is barely used elsewhere on the site to help it stand out.
It could be just a simple link to all the products in your store or if the user needs to enter parameters for their search (such as location and dates in a travel site) it can be part of a module with the relevant fields. Either way, the button should be marked out by a strong colour and it should be obvious what it does with a sensible action word like 'shop' or 'search'.