First of all you need to go to download page (ftp://downloads.swsoft.com/templates) and download Plesk or other application templates for the appropriate OS templates. Actually there are two ways possible to install/upgrade application templates in HSPcomplete.
1. You can do it from Provider Control Center (PCC) at Application Director -> Application templates -> Install application.
2a. In HSPcomplete 3.3 you can install them from the command line using the
/usr/sbin/hspcpkgctl.pl install -d PATH_TO_DIR
script which allows to install multiple templates specifying the directory where the templates are stored.
2b. In HSPcomplete 3.2.X you can install templates from the command line using this script:
/usr/sbin/hspc-install-tmpls.pl -d PATH_TO_DIR
After application templates are installed in HSPcomplete Provider may add them into hosting plans (upgrade subscriptions to the latest version of plan if needed) and templates will be available for installation into VEs.
If VE already has some application template installed then it will be possible to upgrade application to new version either from VE control panel or from PCC on 'Applications' tab in VE properties.