Admin>>Catalog
When you select (click) the catalog tab, you will be presented with a
screen with two core sections displayed, “Categories” which will list
all you current categories and allow you to edit existing or add new
categories and below this “Products in this category” which displays
all the products for the active category. When you first load this page the default category is “home” and thus the products displayed
will be active in the home category. (See below)

click the “Add new subcategory button” and the following screen will be displayed
Edit or add new Category
Name: Enter the name you want for this subcategory
Displayed: Select if you want this category displayed in your store (the default)
Parent Category: If your category will exist inside
another category, for example chairs inside furniture, then select the
furniture category. If this new category is a top level category
however, select home (home is the default and top level category).
Image: If you wish to have a image displayed at the
top of your category page, use the browse button and upload a suitable
sized image.
Meta title: Enter the title for the page. This will be the Search Friendly title displayed in your browser
Meta Description: Enter a suitable meta description.
The meta description is the description your see below the title in
search results pages. Tip: For better search optimisation include your
most important keywords
Friendly URL: The friendly URL is displayed in your
browser address bar. For example if you entered “furniture” the browser
would display www.myshop.com/furniture
If you are using a multi-lingual shop, you will need to select the flag for each language and then enter the appropriate words for each field. Once you are happy with all entries press save.
TIP: In modules >> Category block >> Configure: you can spcify how many levels deep you want sub-categories to be displayed within the "maximum depth field". There is also a option called dynamic. When this is deactivated, the sub categories will be shown on your website. But when dynamic (the default) is selected, you will have a little + to allow your users to expand the sub-categories.
To the right of each category displayed, there are four options.
edit sub-categories
Displayed: Should this category be displayed or not. When you turn off “Displayed” the category will not be shown in the menu. One thing to be aware of is that product in that category will still be shown in the featured products by default, and when a user goes to that product, the breadcrumb navigation will still show the category. If you click this you will get a message “This category is currently unavailable”. Ideally Prestashop should remove the category from the breadcrumb trail by default to stop this issue
View: View the category (clicking on the category
text will also display the category). This view simply displays the
product in the category
Edit: Clicking edit will display the category set-up screen where you
can edit the fields as required (See adding new category for further
details).
Remove (delete) Subcategory:This is the last option and be aware that it is very easy to click and remove a category. There is no un-delete option although a pop-up will confirm that you wish to delete this category first. If you say yes in the pop-up, the category is immediately deleted.
Tip: Prestashop will allow you to delete categories, even if there are products that belong to that category so my recommendation is first to view products in this category and change (re-assign) all these products to another category before you actually delete the category itself.
In both the Back Office and the Front Office, PrestaShop automatically sorts categories alphabetically as they are added. However, you may manually sort categories in the order of your choice by adding a numerical prefix to the category name:
1. In Back Office >> Catalog >> Categories section, locate the category you want to modify.
2. In its Action column, click the Edit icon.
3. In the Category edit page, add the number and then a period (.) before the category name, without spaces.
Tip: Use at least two-digit numbers (e.g., 01, 02, 03). This will help keep categories in the correct order. Use three-digit numbers for stores that contain between 100 and 1000 categories, etc.
For example:
IMAGE
4. Click Save.
5. Repeat steps 1-4 for each category you want to sort.