In order to manage the string resources, go to: Administration > Configuration > Languages
Select t he language for which you would like to add or manage the string resource. In this windows, you will see the list of languages you have installed for your store site.
In the case of this example, we will be choosing "English language":
Click on the link "View string resources":
- From the Select language dropdown list, you can easily filter your results by language
- You can click the "Add new record" button. The window below will be expanded enabling you to add a new record to the grid, as follows:
Make sure to click "UPDATE" to save the changes.