Hi,
Normally, when you install HikaShop it adds a module "latest products" pre configured for that. So you just have to go in the Joomla modules manager and enable the module and change its position to the sidebar position of your template where you want the module to be displayed.
If that module is missing (possible if you deleted it without knowing, or if you used a template starter pack which doesn't have it for example), then you can create a new module instance of the "HikaShop content module" in the Joomla modules manager, and you'll then have to configure the options under the HikaShop options tab so that it displays the latest products.