How to create customer groups in PrestaShop
You can add a customer group from the backend of your store. You can use customer groups for various things. For example, you can put your loyal customers into a group and give that group discounts on some or all products that your store offers, or you can restrict the access to one or more product categories to a specific group or groups.
To create a customer group, log in to the admin panel of your store, then click on the Customers tab. On the home page of the Customers tab you'll see a table with all the registered customers. Click on the Groups submenu that's just below the Customers tab. On the page that opens you'll see a table with the groups. If you haven't created any, there should be only one group called Default. As the name suggest that's the main group to which all customers belong by default. To create a new group click the Add new button that's above the table. Then you have to type a name for the group, and if you want, you can give a discount (in percent) on all the products in your store. The discount will be used by all members of this group. After that click on the Save button to create the group.
After the group is added you can edit it by going to Customers tab>Groups and clicking on the edit icon for the particular group. When you edit a group you can actually add group discounts that will apply only to one product category or subcategory. This can't be done while creating the group, when you can only add a group discount on all products. Keep in mind that the discount on the products in a particular category overwrites the discount that applies to the whole store. So, for example, you've given a 20 percent discount on all products, and you have also added a specific 30 percent discount on the products in a category called Computers. Then the products in the Computers category will be 30 percent cheaper, not 50 or 20, while the rest of the products in the store will have a discount of 20 percent.
At this point the group should be empty. You can add as many members to it as you want. To do this, on the home page of the Customers tab choose the customer you want to add, and click on the edit icon for that customer. This will display the customer's personal information (name, email, etc.). Find the drop-down menu labeled Default customer group and set it to the desired group. Don't forget to click on the Save button.