Install from Web
From Joomla! Documentation
The Joomla Install from Web feature was added as part of 
to make installing extensions from the Joomla! Extensions Directory (JED) easier.
To enable it, go to Administrator → Extensions → Manage → Install → Install from web tab and select the notice at the top to install the plugin that's needed.
Video Demo[edit]
You can see a video walk through of the Install from web feature on YouTube
Information for Extension Developers[edit]
If you already have an extension on JED you need to make a few small changes to get your extension working on the Joomla Extension Finder. Go to the Install From Web For Developers article for more information.
Plugin Version and Revision History[edit]
To see the latest release and the development history of the plugin, go to the Joomla CMS repository at GitHub. Notice that you may select from several branches and tags at the dropdown menu at the upper left corner of the web page. (Usually you'll stay with the default branch.)
Now navigate down through the hierarchy of the Joomla CMS file structure. From the root, select plugins folder → installer folder → webinstaller folder. A link to the commit History is available in the upper right corner of the page.