Imagine a product in your product catalog that you want to connect with one or more other products to recommend and upsell these additional products to customers when they view the first one. To do that, you will need to edit the first product specifying other products related to it. You can do it manually or via import.
Adding Related Products Manually
You can add related products to any product in your catalog.
On the products listing page of your store's Admin area (Catalog -> Products), find the required product and open its details for viewing/editing.
In the Related Products tab, click "Add related products."
You will see a popup with a list of products to select the related products.
Select the product(s) you want to relate to. Use the filter above the list to find the product(s) you require.
Adjust the "Make bidirectional relations" setting at the bottom of the list as you require to specify how the selected products should be related to the main product. (Enable the "Make bidirectional relations" option if you want all chosen products to be interrelated.)
Click Add products.
This adds the selected product(s) as related.
Adding/Updating Related Products via Import
To set product relations via the built-in import feature, use the products.csv file. The file defines the related products SKU in the "relatedProducts" field.
The simplest file for the related products info import may look as follows:
Check CSV Import: Products for details.