Whether installing or updating, whether this plugin or any other, it is always advisable to back-up your data before starting
Unzip allow-multiple-accounts.zip inside the /wp-content/plugins/ directory for your site (or install via the built-in WordPress plugin installer)
Activate the plugin through the 'Plugins' admin menu in WordPress
Go to the Users -> Multiple Accounts admin settings page (which you can also get to via the Settings link next to the plugin on the Manage Plugins page) and configure settings. On a Multisite install, go to My Sites -> Network Admin -> Users -> Multiple Accounts.
Requires: 3.1 or higher Compatible up to: 3.3.2 Last Updated: 2011-7-14 Downloads: 17,214