How to install plugins in Qt Creator?
You can find instructions for installation at the bottom of the webpage of Artistic Code Style plugin:
Quick
Move the downloaded zip/tar.bz2 archive to the root directory of Qt Creator and extract it. After a restart of Qt Creator all should work.
Looks like plugins can be found under .\QtCreator\lib\qtcreator\plugins so if you want to install a plugin you just need to copy the files of the plugin (one dll and one pluginspec) there and (re)start Qt Creator.