You can easily open (connect to) a plugin file system from the Change Drive Menu and from the Drive Bar. If you do not find a file system in this menu or bar, find the appropriate plugin in the Plugins Manager dialog box and select the Show FS item in Change Drive menu and Drive bar check box. Also see Changing Directory for other ways to open (change directory to) a plugin file system, mainly Commands/Change Directory (Shift+F7) and Edit/Paste (Ctrl+V).
When you open a file system in a panel, you can work with the files and directories in it. Focus or select them and use View, Copy, and Move (it works in both directions, to and from the other panel), Delete, Copy to and Paste from clipboard, Compare Directories, and other commands (see the menu for enabled commands). You can also use commands from the context menu (right-click or Shift+F10).
The View command copies the focused file from the plugin file system to a temporary directory. The file is then opened in the Viewer. The plugin can use a cache for such files, so if you try to view the file a second time, it is displayed from the temporary directory. To get the most recent version of the file, use Refresh.