What do you mean by skill string? Changing skill name that applies ingame? If that's the case - go on your Ran Client folder and look for "data" folder, next step go on "ui" folder and look for skillstrtable.xml file, next step open the .xml file and edit it with some text editor. Mine I'm using VS Code IDE so that I can easily look for the skill value I'm looking for.
After that save the file, and that's all...