Sitecore commerce The product catalog is not associated to this inventory catalog

In the process of setting up a a demo commerce site in Sitecore, the following error occurred when attempting to use my new catalog.

[System Error: The product catalog is not associated to this inventory catalog.]

In my case, there was a base catalog (which contained the products and categories). But not an inventory catalog. To fix this error, load up the merchandising manager, and go to the inventory catalog tab.

Sitecore merchandising manager, inventory catalog tab

After creating an inventory catalog, you simply associate it with a product catalog.

Sitecore commerce, associate inventory catalog with product catalog

You are now able to add inventory to products and the error above will not occur.