To set sorting options, you have to:

1. Log in to Administration Panel
2. Go to "Settings" cart in "Configurations" tab
3. Go to "General" section  and choose "Catalog" option
4. Przejść do panelu filters_and_sorting
5. In the upper part of the panel, select from the drop-down list the option "Form"
6. When you click on "enableSortCriteria", a drop-down list will appear in which you can select the sorting options that will be available to end user. 
7. After selecting the sorting option settings, save the changes by clicking the "Update" button next to the section

 Sorting options to choose:

• RANK_DESC - Sorting by product order quantity 
• NAME_ASC - Sorting by product name from A to Z 
• NAME_DESC - Sorting by product name from Z to A 
• MANUFACTURER_ASC - Sorting by manufacturer name from A to Z 
• MANUFACTURER_DESC - Sorting by manufacturer name from Z to A 
• STOCK_ASC - Sorting by product availability from the least amount
• STOCK_DESC - sorting by product availability from the biggest amount
• NET_PRICE_ASC - Sorting at net price of products from the lowest
• NET_PRICE_DESC - Sorting at net price of products from the highest
• GROSS_PRICE_ASC - Sorting at gross price of products from the lowest
• GROSS_PRICE_DESC - Sorting at gross price of products from the highest