Hi,
Normally, you have a module called "related products" which is preinstalled with HikaShop. And normally, it is preselected in the "modules under the product page" setting of the HikaShop configuration.
So all you have to do is to add products as related products in your products and they will appear on the product page of your products.
If that's not the case, the first thing is to check that setting in the HikaShop configuration. Do you have a "related products" module selected there ?
If no, check if you see it in the list of available modules. If no, you'll have to create it via the Joomla modules manager by creating a new module instance of the module "HikaShop content modules" and then selecting it in that setting.
If yes, then check the settings of your module via the Joomla modules manager. The key points are that the "relation" setting should be set to "related products" and the "synchronize" option should be activated under the "HikaShop options" tab of your module.
Here is a screenshot of the settings of the module on our demo website and how these settings are by default when HikaShop is first installed on a website:
monosnap.com/file/cOIiPR5DFigIowx9H794nVVMzkF7fX
So you can take this as a reference if you need to recreate the module or check its settings.
