This plugin used to easily add an ajax enabled wordpress login widget to your site's sidebar.
To do a new installation of the plugin, please follow these steps 1. Unzip and upload the php file to your wordpress plugin directory 2. Activate the plugin 3. For a wp sidebar widget: Goto the design > widgets tab - Drag the widget into a sidebar and save!
Check more details about installation and usage here
To use the template tag: Add <?php sidebarlogin(); ?> to your template.
You will find a config page in tools/settings > WP Sidebar Login. Here you can set links and redirects up.