Usually, modules in PrestaShop must be configured before the usage. Pretty clean urls extension also requires configuration before the usage. Below you can find informations about sections where you can configure the addon. Clean urls addon from mypresta.eu is easy to configure and it is not necessary to prepare some advanced settings, because everything - module does automatically.
To get more informations about configuration process - go to the next step of this document where I describe configuration process of the addon.