Once you have added a category, it is simple to add a sub-category to it.
- Go to https://yourmarketplacename.arcadier.io/admin
- Log in using your credentials
- Click on "Configuration", then "Categories"
- Click on the “Add a Category” sign
- Insert the name of your new sub-category.
- Select the "parent" category
- Click on the tick box and.. Voila!
To change the relative positions of your sub-categories, simply click on the arrows to shift the position up or down