Activating Flags in the menu

Hi I just installed polylang on a new website http://www.agenturaprevas.sk/uvod/ and I’ve used it before and worked great.

Now, when I add the 2 menus under Appearance/Menus it doesn’t give me an option where it says Language switcher – not sure if I missed some settings? I would like to add the flags to the navigation menus.

Thank you

https://wordpress.org/plugins/polylang/