To enable a product to appear in the 'Specials' module, firstly the 'specials' module will need to be activated and positioned on the home page

• Log in to prestashop admin
• In the menu, click 'Modules', then 'Module Manager'
• Search for 'special'
• Your theme may have its own specials module, if so, enable this otherwise, enable the default 'specials block' module
• Check your home page to ensure the module appears in the correct location, if not, it will need to be positioned via: Menu → Design → Theme & Logo → Pages Configuration