Click "Add Extension", choose siteprobuilder.zip (the file you just downloaded) file and click "OK"
When installation is complete... you are ready to go.
NOTE! The plugin works only for customers but not for users of customers. The user will get error "Permission denied".
NOTE! Make sure that passive mode in FTP server is enabled. Usually it is disabled by default.
NOTE! When updating "Limited plans" field in the license the plugin needs to be re-installed.
Note! If plugin throws "Access denied" or "Permission denied" error then check what mode your panel is on. Go to "Tools & Settings" -> "Interface management". If your panel is on "Power user view" mode then switch it to "Service provider view". After that the plugin will work however only for newly created customers. So you will need to remove all users created in Power user view mode and create them anew as Customers in Service provider view.
About Plesk / Plesk Onyx
Professional control panel that gives web-designers, web-masters and website owners tools to manage their servers, sites and applications. Parallels / Odin is a global leader in hosting and cloud services enablement and cross-platform solutions. The Parallels Plesk / Plesk Onyx Panel software package is a commercial web hosting automation program.