The beta version of the Semi-Automatic Classification Plugin v.4.0 "Frascati" is available through the the Facebook group and the Google+ Community. The main new features of the plugin are described in my previous post here.
In order to install the beta version:
1. download the zip file from here;
2. open the directory .qgis2/python/plugins that is inside the User/Home directory and delete the folder SemiAutomaticClassificationPlugin if present;
3. extract the downloaded zip file inside the directory .qgis2/python/plugins;
4. the plugin should be installed; start QGIS, open the Plugin Manager and be sure that Semi-Automatic Classification Plugin is checked.
Following the video illustrating the main new features of SCP 4.0.