It is installed like any other plugin? You need to go to the Administration->Plugin Center and make sure the plugin name is on that menu. That effectively "installs" the plugins, once you've uploaded the directory.
Once that is done, then (for the template editor) you need to set the right permissions, which can be done on "site users", and then click on the user you want to allow access to the plugin, and then you will probably see all but one checkbox in the permission checkboxes at the bottom of the screen. Once you enable the checkbox, then you can go edit the templates, either the site-wide templates under Administration, or blog-specific templates under the control panel.