I’m sorry, i forgot to mention that the google code site is a source-file repository, there all files are already displayed unpacked (not as xrnx archive but simply displays in their native folder)
You have a “Scripts” folder in your preferences folder (Help → Show preferences folder) there go to Scripts\Tools\com.renoise.SampleSlicer.xrnx\ and copy the .lua file over there.
You might have to disable and (re)enable the tool in the “Toolbrowser” to allow it reloading the tool though, or enable the scripting-dev option so that you get an extra option in the tools menu called “Reload all tools” see: How To Manually Install Xrnx Files It is a bit more cumbersome method to do it manually, but it works.