Find the string you want to change, and edit the text.
Tip. use your browsers "find" tool (usually ctrl-f) to help search through the entries.
In this example, we will change the text on the "Minicart icon" from "Shopping Bag" to just "Bag".
Save the changes. Any changed strings are marked with a small icon so they can be easily spotted later. Hovering over this icon shows the original text, and clicking it will restore the original text.
Applying the text changes to your shop.
Click "Manage" and scroll down to the "localization script" box. Copy this code and put it into your shop page html. See the Ecwid FAQ for how to do this; e.g. see this section for a Wordpress based site.
Applying the text changes to your store on Facebook
Unfortunately, this is not possible to do in a simple reliable way right now.
See this forum post (the response by Lana to point 5) 01-04-2014, 09:59 AM).