We are using MailChimp for WP plugin for Newsletter subscribe. You can read more about MailChimp from here
Follow that step below to help you can collect email of subscribers.
Step 3 - Navigate to MailChimp for WP > MailChimp then connect with your mailchimp account you created from step 1
Step 4 - Create mailchimp form to collect email. Navigate to Forms
Import HTML Code below on section Form mark-up Source
<h3>Get The Latest</h3>
<p>Sign up for our Newsletter to get the Latest on all things suitMe.</p>
<p><input id="mc4wp_email" class="form-control" name="EMAIL" required="required" type="email" placeholder="Your Email " /></p>
<p><button class="mc4wp-btn btn" type="submit" value="Join">Join <i class="fa fa-angle-double-right" aria-hidden="true"></i></button></p>
Step 5 - After creating from of your plugin. You must set position where you want to display.
Going Appearance -> Widgets then drag mailchimp widget to Newsletter Sidebar. You can bring that sidebar to every position you want. ( You can drag to left, right sidebar for each page. You can drag to Footer position.... )