Install the plugin by other copying the plugin to your ‘plugins’ folder or through
WordPress’ plugin repository. Then to use it either use the ‘Subscription Form’ and ‘Unsubscription Form’
widgets or the following shortcodes ‘[subscribe-now-subscribe-form]’ or ‘[subscribe-now-unsubscribe-form]’
to get respectively the subscribe and unsubscribe forms.
Tested up to: 5.4.2