1, With your PrestaShop admin panel, go to the International > Translations section to edit the notification.
2, With the Modify Translations section, choose the ‘Themes translations‘ option for the Type of translation. Select the YourTheme and choose the language to which you will translate to.
3, Click the Modify button at the right bottom corner.
4, Use Ctrl+ F hotkey (F hotkey for Mac) to find the %copyright% %year% – Ecommerce software by %prestashop%.
5, Change the translation according to your needs and save the changes.