To install plugin update, you can follow this step :
After installing updated themes, you will get notice if your plugin is out of date
You can go to WordPress Admin Panel > Plugin, and deactive your plugin, then delete out of dated plugin (make sure you delete plugin that come with the themes).
You will noticed to install new plugin, go to WordPress Admin Panel > Appearance > Install Plugin. and begin to install your plugin.
But now there is NO update of the jkreativ plug-in anywhere in the Admin Panel > Appearance > Install Plugin !