How to display related products

I know this is a basic problem, but I cannot work out what I have done wrong. I'm not sure where to post this question...
I have created a HikaShop Content Module in Joomla modules to display related products.
My problem is that this displays random products in the category listing and the products listings. I only want it to display the "related products" that I chose to go with individual products.
I have tried unpublishing the module, but then no related products show.
I'd be grateful if someone can tell me what simple mistake I have made!

Hi,

By default when installing HikaShop there is a module created, the "Related products" so you can just enable it.
If you no more have this module, so in the settings of the one you have confgured select "related product" for the option "Content on product page", enable "Synchronize with currently displayed item when possible".

And in the product edition page, don't forget to add related items in the one you are editing.