There isn’t a “Send All” button. You choose the intended recipients from the list of available recipients. The “Test” email is on the Settings page (Dashboard > Settings > Email Users) where you can also change the default notification message.
To send an email to users or groups, use the Dashboard > Email Users > Send to Users or Dashboard > Email Users > Send to Groups menu choices. If the target recipient boxes are empty, it means none of your users are configured to receive email. You can fix that on the Dashboard > Email Users > User Settings menu.
I cannot find a way to add users in the Users Settings. Please help. All I see is Bulk Actions but no “add” button
Oh, am I confused? I am the only user on this site. I need a plugin that can send emails to people who have signed up for my newsletter.
You add users to WordPress using the standard WordPress functionality. Email Users does not handle user creation. It adds the necessary meta data to users that already exist and can also be configured to do so for all new users added.
Email Users can only do that if you create a user for all of your recipients. Something like MailChimp (there is a WP plugin too) might be a better solution if you don’t want to have users in your WordPress site.