Product categories are made up of parent category and sub category. It is possible for parent categories to have no sub category or even multiple sub categories.
Every time you create a new category, it will automatically be the parent category. If you want to create a sub category, you will need to assign it to a parent category.
Here's how to create a category:
Login to your Online Dashboard
Choose "Assortment" > "Categories" from the left-side column
Click on the "+ Add category" button in the top right corner
A blank form for a new category will appear. Fill in the category name and choose a category colour.
In this case, we want to make "Fish" as a sub category. Thus, we need to select a parent category from the existing categories that we have (for example: Food).
Now Fish is belong to Food category. If everything looks correct, click the "Save" button to save the parent and sub categories.
To display the new categories on the POS, log in to the app and on your tablet and go to Menu > Settings > Account > Refresh Products