Download and install the Free version from WordPress Plugins Repository
Activate the plugin within your WP-Admin
By default you will have a single Default Local Mailing List in the plugin which will be storing your visitor information.
You can add as many Local Mailing Lists as you want.
If you want to store visitor’s information in your own MailChimp, Aweber or GetResponse account, you will have to activate it first.
Go to Opt-in Samurai in your WP-Admin area > 3rd Party Integration page.
Click Activate button under any service’s logo ie; MailChimp, Aweber or GetResponse